JP5146492B2 - Dielectric ceramic composition and manufacturing method thereof - Google Patents

Description

  The present invention relates to a dielectric ceramic composition and a method for producing the same.

  In recent years, there is a high demand for downsizing of electronic components due to higher density of electronic circuits. Accordingly, for example, multilayer ceramic capacitors have been downsized and increased in capacity, but further improvement in characteristics is required.

  In response to such demands, the dielectric ceramic composition is intended to improve characteristics by allowing the main component and components other than the main component to exist.

For example, Patent Document 1 describes a dielectric ceramic composition in which secondary phase particles containing ABO ₃ as a main component and a crystalline composite oxide containing rare earth elements, Mg, Si and Mn as a main component exist. Yes. It is described that this dielectric ceramic composition can improve temperature characteristics and reliability.

Further, Patent Document 2 describes a dielectric ceramic composition containing ABO ₃ as a main component and containing a rare earth element and Si and a complex compound different from the main component. It is described that this dielectric ceramic composition can improve temperature characteristics and reliability.

  Further, in Patent Document 3, a dielectric comprising a main crystal particle made of a perovskite complex oxide containing Ba and Ti and a grain boundary phase containing Y and Mg, and Mn is present only in the main crystal particle. A body porcelain composition is described. It is described that this dielectric ceramic composition can improve the CR product.

  However, in the dielectric ceramic compositions described in Patent Documents 1 to 3, the improvement in reliability is insufficient, and characteristics under high electric field strength have not been considered.

JP 2007-63114 A JP 2004-155649 A JP 2000-335966 A

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a dielectric ceramic composition that exhibits good DC bias characteristics while improving reliability and a method for manufacturing the same.

In order to achieve the above object, the dielectric ceramic composition according to the present invention comprises:
A compound represented by the general formula ABO ₃ (A is Ba alone or at least one selected from Ba and Ca and Sr, and B is Ti);
An oxide of Zr;
R element oxide (wherein R element is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) And)
A dielectric porcelain composition containing an oxide of Mg,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary existing between two adjacent dielectric particles;
The maximum value of the content ratio of the R element in the crystal grain boundary is Rmax, the region in which the content ratio of the R element in the dielectric particles is 50% or more of Rmax is a diffusion region, and the diffusion in the dielectric particles The area other than the area is the central area,
When the content ratio of Zr in the central region is Zr0, the content ratio of Zr in the diffusion region is Zr1, and the content ratio of Zr in the crystal grain boundary is Zr2, Zr1>Zr2> Zr0 and Zr1 / Zr2 ≧ 1.5 Satisfied with a relationship
The ratio of the dielectric particles satisfying the relationship is 50% or more based on the number of dielectric particles as a whole.

  In the present invention, the presence state of Zr in the crystal grain boundary and the dielectric particles is controlled as described above, and the content ratio of Zr in the diffusion region is made larger than the content ratio of Zr in the crystal grain boundary. By doing so, it is possible to obtain a dielectric ceramic composition that improves the reliability and exhibits good DC bias characteristics.

  Preferably, the dielectric ceramic composition contains an oxide of at least one element selected from Mn, Cr, Co, Fe and Cu.

  Preferably, the dielectric ceramic composition contains an oxide containing Si.

  Preferably, the oxide of Zr is contained in an amount of 0.5 mol or more in terms of Zr element with respect to 100 mol of the compound.

  By using the dielectric ceramic composition having the above composition, the effect of the present invention can be further enhanced.

In addition, the method for producing a dielectric ceramic composition according to the present invention includes:
A compound represented by the general formula ABO ₃ (A is Ba alone or at least one selected from Ba and Ca and Sr, and B is Ti);
An oxide of Zr;
R element oxide (wherein R element is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) And)
A method for producing a dielectric ceramic composition containing an oxide of Mg,
Calcining the raw material of the Zr oxide and the raw material of the Mg oxide to obtain a post-reaction raw material containing an Mg—Zr—O solid solution;
Adding a raw material of the compound to the post-reaction raw material to obtain a dielectric raw material;
Firing the dielectric material, and
In the step of obtaining the post-reaction raw material, the calcining temperature is 900 to 1350 ° C., and the temperature lowering rate after calcining is 200 ° C./hour or more.

  According to the present invention, the presence of Zr in the dielectric ceramic composition can be made desired by using the post-reaction raw material containing the Mg—Zr—O solid solution.

  The electronic component having a dielectric layer in which the dielectric ceramic composition according to the present invention is suitably used is not particularly limited, but it is a multilayer ceramic capacitor, a piezoelectric element, a chip inductor, a chip varistor, a chip thermistor, a chip resistor, and other surface mounting. (SMD) chip type electronic components are exemplified.

  ADVANTAGE OF THE INVENTION According to this invention, the dielectric ceramic composition which improves reliability and shows a favorable DC bias characteristic by making the presence state of Zr into a predetermined thing is provided.

  Further, the presence state of Zr can be controlled by reacting the raw material of the Zr oxide and the raw material of the Mg oxide to produce a post-reaction raw material containing the Mg—Zr—O solid solution.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the dielectric layer 2 shown in FIG. 3A and 3B are schematic diagrams for explaining a method of measuring Zr0, Zr1 and Zr2 by distinguishing the diffusion region and the central region in the dielectric particles. FIG. 4 is a diagram schematically showing the existence state of Zr in the dielectric particles contained in the dielectric ceramic composition according to the embodiment of the present invention.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

Multilayer ceramic capacitor 1
As shown in FIG. 1, the multilayer ceramic capacitor 1 includes a capacitor element body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. At both ends of the capacitor element body 10, a pair of external electrodes 4 are formed which are electrically connected to the internal electrode layers 3 arranged alternately in the element body 10. The shape of the capacitor element body 10 is not particularly limited, but is usually a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use.

Dielectric layer 2
The dielectric layer 2 is composed of a dielectric ceramic composition according to this embodiment. The dielectric ceramic composition comprises, as a main component, a compound represented by the general formula ABO ₃ (A is Ba alone or at least one selected from Ba and Ca and Sr, and B is Ti). As subcomponents, an oxide of Zr, an oxide of R element, and an oxide of Mg are included. The amount of oxygen (O) may be slightly deviated from the stoichiometric composition of the above formula.

The compounds, specifically, expressed by a composition formula _{(Ba 1-x-y Ca} x Sr y) TiO 3, which is a compound having a perovskite crystal structure. That is, at least Ba is included as the A site atom. In addition, the molar ratio between the A site atoms (Ba, Sr and Ca) and the B site atoms (Ti) is expressed as an A / B ratio. In this embodiment, the A / B ratio is 0.98 to 1.02 is preferred. In addition, although both x and y are arbitrary ranges, it is preferable that it is the following ranges.

  In the present embodiment, x in the above formula is preferably 0 ≦ x ≦ 0.5. x represents the number of Ca atoms, and by setting x within the above range, the capacity temperature coefficient and the relative dielectric constant can be arbitrarily controlled. If x is too large, the dielectric constant tends to be low. In the present embodiment, Ca may not necessarily be included.

  In the present embodiment, y in the above formula is preferably 0 ≦ y ≦ 0.5. y represents the number of Sr atoms, and the relative permittivity at room temperature can be improved by setting y within the above range. If y is too large, the dielectric constant tends to decrease. In the present embodiment, Sr does not necessarily have to be included.

  In this embodiment, the B site atom is only Ti, but an element other than Ti (for example, Zr or Hf) may be contained in the B site atom as long as the amount of impurities is about. In this case, the impurity amount can be made 0.3 atomic% or less with respect to 100 atomic% of B site atoms.

The content of the oxide of Zr is preferably 0.5 to 50 mol and more preferably 2 to 30 mol in terms of Zr element with respect to 100 mol of the compound represented by ABO ₃ . If the content of the Zr oxide is too small, the presence state of Zr tends not to be a predetermined one, while if too much, the firing temperature tends to increase.

In this embodiment, the oxide of Zr may be in the form of a composite oxide containing other metal elements, but it includes a load imposed on the manufacturing process by the composite oxide synthesis process and a composite oxide. In consideration of the influence on the electrical characteristics due to this, it is preferably in the form of ZrO ₂ .

The content of the oxide of R element is preferably 0.5 to 10 mol, more preferably 1 to 5 mol in terms of R element with respect to 100 mol of the compound represented by ABO ₃ . When the content of the R oxide is too small, the high temperature accelerated life tends to decrease. On the other hand, if the amount is too large, the relative permittivity tends to decrease. The R element is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. At least one selected from Gd, Tb is preferable, and Y is particularly preferable.

The content of Mg oxide is preferably 0.2 to 20 mol, more preferably 0.5 to 3 mol in terms of Mg element, with respect to 100 mol of the compound represented by ABO ₃ . If the Mg oxide content is too small, the temperature dependence of the relative permittivity tends to increase, whereas if it is too large, the relative permittivity tends to decrease.

  In the present embodiment, other components may be contained as necessary.

Specifically, the dielectric ceramic composition may contain, for example, an oxide of at least one element selected from Mn, Cr, Co, Fe, and Cu. The content of these oxides is preferably 0.05 to 5 mol, more preferably 0.1 to 2 mol, in terms of each element, with respect to 100 mol of the compound represented by ABO ₃ . If the content of the oxide is too small, IR tends to decrease, while if too large, the relative dielectric constant tends to decrease. Among the above oxides, it is preferable to use an oxide of Mn and / or an oxide of Cr because the effect of improving the characteristics is great.

The dielectric ceramic composition may contain an oxide containing Si. The oxide containing Si mainly has a role as a sintering aid. The content of these oxides is preferably 0.5 to 10 mol in terms of Si element with respect to 100 mol of the compound represented by ABO ₃ . When the content of the oxide is too small, the sinterability tends to deteriorate. On the other hand, if the amount is too large, the relative permittivity tends to decrease. The oxide containing Si is preferably an oxide of Si or a composite oxide of Si and at least one selected from Li, B, Al, Ba and Ca, and (Ba, Ca) SiO ₃ is more preferable. preferable.

  The thickness of the dielectric layer 2 is not particularly limited, and may be determined as appropriate according to desired characteristics and applications.

Structure of Dielectric Particles In this embodiment, the dielectric particles 20 contained in the dielectric ceramic composition constituting the dielectric layer 2 are composed of R elements and Zr elements with respect to the main component particles (ABO ₃ particles). And Mg elements (subcomponent elements) are solid solution (diffusion) particles.

As shown in FIG. 2, the dielectric particle 20 includes a central region 20a substantially composed of a main component (ABO ₃ ) and components other than the elements constituting the main component that exist around the central region 20a. And a diffusion region 20b diffused in the region. A crystal grain boundary 21 exists between two adjacent particles.

  In the present embodiment, the crystal grain boundary 21 is defined as a boundary region existing between two particles. Therefore, a region 22 (such as a triple point) existing between three or more grains is not included in the crystal grain boundary 21.

  The central region 20a is substantially composed of the main component. On the other hand, in the diffusion region 20b, R element, Zr, Mg, etc. are diffused (solid solution) in the main component. In the present embodiment, not only the R element, Zr and Mg but also other elements may exist in the diffusion region 20b.

  In the present embodiment, the central region 20a and the diffusion region 20b in the dielectric particle 20 may be distinguished as follows, for example.

  First, a predetermined number of dielectric particles are observed with a scanning transmission electron microscope (STEM), and using an attached energy dispersive X-ray spectrometer (EDS), as shown in FIG. A point analysis is performed at the crystal grain boundary 21 in the vicinity of 20 outer edges. Among the contents of the R element obtained by analyzing the characteristic X-rays obtained by the analysis, the highest value is defined as Rmax.

  The number of measurement points is not particularly limited, but is preferably 10 or more per dielectric particle. Further, the number of dielectric particles to be measured is not particularly limited, but is preferably 10 or more, for example.

  Subsequently, in the dielectric particle 20, by mapping the R element mapping image, a region where the R element content is 50% or more of Rmax and a region where the R element content is less than 50% of Rmax. And divide into That is, as shown in FIG. 3B, a region of 50% or more of Rmax is defined as a diffusion region 20b, and a region of less than 50% of Rmax is defined as a central region 20a.

  By doing so, the center region 20a and the diffusion region 20b in the dielectric particle 20 can be clearly distinguished.

  Next, the characteristic X-rays at the crystal grain boundaries 21 obtained above are analyzed to calculate the Zr content ratio, and the average value is taken as the Zr content ratio (Zr2) at the crystal grain boundaries 21.

  Further, in the same manner as described above, point analysis is performed in the diffusion region 20b as shown in FIG. The average value of the obtained Zr content is defined as the Zr content (Zr1) in the diffusion region 20b.

  Further, the same analysis is performed on the central region 20a, and the Zr content ratio (Zr0) in the central region 20a is calculated.

  Note that the number of measurement points and the number of dielectric particles to be measured when obtaining Zr0, Zr1, and Zr2 may be the same as in the case of the R element.

  Zr0, Zr1 and Zr2 thus obtained satisfy the relationship of Zr1> Zr2> Zr0 and Zr1 / Zr2 ≧ 1.5 in this embodiment. Moreover, it is preferable that 2 ≦ Zr1 / Zr2 ≦ 5. That is, as shown in FIG. 4, the content ratio of Zr increases from the center region 20a to the diffusion region 20b of the dielectric particle 20, and the content ratio of Zr decreases from the diffusion region 20b to the crystal grain boundary 21. It becomes a structure and the peak of the content rate of Zr exists in the diffusion region 20b.

  Further, in this embodiment, the dielectric particles 20 whose Zr content ratio satisfies the above relationship are 50% or more, preferably 60% or more, more preferably 70% or more, based on the number of the dielectric particles. It is.

  By making the existence state of Zr characteristic as described above, it is possible to improve reliability and improve DC bias characteristics.

As described above, since the central region 20a is a region substantially made of ABO ₃ , Zr0 usually does not become larger than Zr1 and Zr2. Therefore, when it is clear that Zr0 is smaller than Zr1 and Zr2, measurement of Zr0 can be omitted.

  In the above description, Rr is calculated and then Zr0, Zr1 and Zr2 are calculated. However, these may be calculated simultaneously.

  Although the relationship between Zr0, Zr1, and Zr2 described above will be described later, by controlling the calcining conditions, the content of Zr, and the like, the diffusion of Zr can be controlled and a desired presence state can be realized.

  The crystal particle diameter of the dielectric particles contained in the dielectric layer 2 is measured as follows. That is, the capacitor element body 10 is cut in the stacking direction of the dielectric layer 2 and the internal electrode layer 3, the average area of the dielectric particles is measured in the cross section, the diameter is calculated as the equivalent circle diameter, and the value multiplied by 1.5 It is. The measurement was performed on 200 or more dielectric particles, and the value at which the accumulation was 50% from the cumulative frequency distribution of the obtained particle diameter was defined as the crystal particle diameter (unit: μm).

  In the present embodiment, the crystal particle diameter may be determined according to the thickness of the dielectric layer 2 and the like.

Internal electrode layer 3
The conductive material contained in the internal electrode layer 3 shown in FIG. 1 is not particularly limited, but a relatively inexpensive base metal can be used because the constituent material of the dielectric layer 2 has reduction resistance. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more elements selected from Mn, Cr, Co and Al, and the Ni content in the alloy is preferably 95% by weight or more. In addition, in Ni or Ni alloy, various trace components, such as P, may be contained about 0.1 wt% or less. The internal electrode layer 3 may be formed using a commercially available electrode paste. What is necessary is just to determine the thickness of the internal electrode layer 3 suitably according to a use etc.

External electrode 4
The conductive material contained in the external electrode 4 shown in FIG. 1 is not particularly limited, but inexpensive Ni, Cu, and alloys thereof can be used in this embodiment. What is necessary is just to determine the thickness of the external electrode 4 suitably according to a use etc.

Manufacturing Method of Multilayer Ceramic Capacitor 1 The multilayer ceramic capacitor 1 of the present embodiment is the same as a conventional multilayer ceramic capacitor. After producing a green chip by a normal printing method or a sheet method using a paste and firing it, It is manufactured by printing or transferring an external electrode and firing. Hereinafter, the manufacturing method will be specifically described.

  First, a dielectric material for forming a dielectric layer is prepared, and this is made into a paint to prepare a dielectric layer paste.

As dielectric materials, first, an ABO ₃ material, an R element oxide material, a Zr oxide material, and an Mg oxide material are prepared. As these raw materials, oxides of the above-described components, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above-described oxides or composite oxides by firing, such as carbonates and oxalic acid. They can be appropriately selected from salts, nitrates, hydroxides, organometallic compounds, and the like, and can also be used as a mixture.

In addition to the so-called solid phase method, the raw material of ABO ₃ can be produced by various methods such as those produced by various liquid phase methods (eg, oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.). What was manufactured can be used.

  Moreover, when components other than the above components are contained in the dielectric layer, raw materials for the components are prepared. As these raw materials, oxides of those components, mixtures thereof, and composite oxides can be used as described above. In addition, various compounds that become oxides or composite oxides by firing can be used.

  In order to prepare a dielectric material, first, a Zr oxide material and a Mg oxide material are reacted to obtain a post-reaction material containing a Mg—Zr—O solid solution. It is not necessary to react the entire amount of the Zr oxide raw material and the Mg oxide raw material into an Mg—Zr—O solid solution, and the post-reaction raw material includes not only the Mg—Zr—O solid solution. Further, an unreacted Zr oxide raw material and / or an Mg oxide raw material may be contained.

The method for obtaining the Mg—Zr—O solid solution is not particularly limited, but in this embodiment, the Zr oxide raw material and the Mg oxide raw material are calcined. At this time, it may be calcined in a state in which a raw material of an auxiliary component other than the raw material of the Zr oxide and the raw material of the Mg oxide (R element oxide raw material and other component raw materials) is included. And calcination in a state in which no ABO ₃ raw material is contained.

  The calcining conditions may be as follows. The calcination temperature is 900 to 1350 ° C., preferably 1200 to 1350 ° C., the holding time is preferably 1 to 5 hours, and the temperature lowering rate after elapse of the holding time at the calcination temperature is 200 ° C./hour or more, preferably 300 ° C./hour More than time, more preferably 400 ° C./hour or more.

By setting it as such calcining conditions, the raw material after calcining (calcining raw material) contains a Mg—Zr—O solid solution. According to MgO-ZrO ₂ system phase diagram, at about 900 ° C. or higher, MgO is dissolved to ZrO ₂ of about 10 mole%, at about 1300 ° C. or higher, it can be dissolved to ZrO ₂ of about 30 mol% Are known.

Therefore, the Mg—Zr—O solid solution is generated by setting the calcining temperature within the above range. However, when the rate of temperature decrease after the holding time at the calcining temperature is small, the phase is separated into MgO and ZrO ₂ according to the MgO—ZrO ₂ phase diagram as the temperature decreases.

Therefore, in this embodiment, it cools to normal temperature in the state which maintained the Mg-Zr-O solid solution by making the temperature-fall rate after holding time progress by calcining temperature into said range. Presence of a part of Zr which diffuses from Mg-Zr-O solid solution to ABO ₃ particles by producing a dielectric ceramic composition using a calcined raw material containing such Mg-Zr-O solid solution You can control the state. As a result, it becomes easy to set Zr0, Zr1 and Zr2 within the above-described range.

  In the present embodiment, the temperature lowering rate is calculated based on the time required to lower the temperature from the maximum temperature during calcination to 600 ° C.

Note that even if a dielectric ceramic composition is manufactured using phase-separated MgO and ZrO ₂ , the diffusion of Zr cannot be controlled, and the effects of the present invention cannot be achieved.

Further, in the process of manufacturing the dielectric ceramic composition, a part of Mg and Zr diffuses from the Mg—Zr—O solid solution, but the Mg—Zr—O solid solution exists in the fired dielectric ceramic composition. doing. Note that Mg diffusing into the ABO ₃ particles is in a diffusion state different from Zr. Specifically, the Mg content ratio (Mg0) in the central region, the Mg content ratio (Mg1) in the diffusion region, and the Mg content ratio (Mg2) in the grain boundary satisfy the relationship of Mg2>Mg1> Mg0. To do.

  By satisfying the above relationship, the Mg content increases from the grain center toward the grain boundary, so that grain growth of the dielectric particles is suppressed, and as a result, the lifetime is improved. In other words, the above relationship is advantageous in terms of life compared to a configuration satisfying the relationship of Mg2 <Mg1.

The calcined raw material (post-reaction raw material) thus obtained is pulverized as necessary. The pulverization time is preferably 5 hours or more when the calcination temperature is 950 to 1200 ° C., and preferably 24 hours or more when the calcination temperature is 1200 to 1350 ° C. Thereafter, the calcined raw material and the remaining raw materials (ABO ₃ raw material and subcomponent raw material not calcined) are mixed to obtain a dielectric raw material.

  In addition, what is necessary is just to determine content of each component in a dielectric material so that it may become a desired composition after baking.

  Next, the dielectric material is made into a paint to prepare a dielectric layer paste. The dielectric layer paste may be an organic paint obtained by kneading a dielectric material and an organic vehicle, or may be a water-based paint.

  An organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. The organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, toluene, and the like according to a method to be used such as a printing method or a sheet method.

  Further, when the dielectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder or a dispersant is dissolved in water and a dielectric material may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, etc. may be used.

  The internal electrode layer paste is obtained by kneading the above-mentioned organic vehicle with various conductive metals and alloys as described above, or various oxides, organometallic compounds, resinates, etc. that become the above-mentioned conductive materials after firing. Prepare.

  The external electrode paste may be prepared in the same manner as the internal electrode layer paste described above.

  There is no restriction | limiting in particular in content of the organic vehicle in each above-mentioned paste, For example, what is necessary is just about 1-5 weight% of binders, for example, about 10-50 weight% of binders. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. The total content of these is preferably 10% by weight or less.

  When the printing method is used, the dielectric layer paste and the internal electrode layer paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip.

  In the case of using the sheet method, a green sheet is formed using a dielectric layer paste, and after printing the internal electrode layer paste thereon, these are stacked, cut into a predetermined shape, and formed into a green chip. .

  Before firing, the green chip is subjected to binder removal processing. As binder removal conditions, the temperature rising rate is preferably 5 to 300 ° C./hour, the holding temperature is preferably 180 to 400 ° C., and the temperature holding time is preferably 0.5 to 24 hours. The binder removal atmosphere is air or a reducing atmosphere.

  After removing the binder, the green chip is fired. In firing, the rate of temperature rise is preferably 100 to 800 ° C./hour. The holding temperature during firing is preferably 1300 ° C. or less, more preferably 1200 to 1280 ° C., and the holding time is preferably 0.5 to 8 hours, more preferably 1 to 3 hours. If the holding temperature is lower than the above range, the densification becomes insufficient. If the holding temperature exceeds this range, the electrode is interrupted due to abnormal sintering of the internal electrode layer, the capacity-temperature characteristic is deteriorated due to diffusion of the constituent material of the internal electrode layer, and the dielectric Reduction of the body porcelain composition is likely to occur.

The firing atmosphere is preferably a reducing atmosphere. As the atmosphere gas, for example, a mixed gas of N ₂ and H ₂ can be used by humidification.

In addition, the oxygen partial pressure during firing may be appropriately determined according to the type of the conductive material in the internal electrode layer paste, but when a base metal such as Ni or Ni alloy is used as the conductive material, The oxygen partial pressure is preferably 10 ⁻¹⁴ to 10 ⁻¹⁰ MPa. When the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may be abnormally sintered and may be interrupted. Further, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized. The rate of temperature drop during firing is preferably 50 to 500 ° C./hour.

  After firing in a reducing atmosphere, the capacitor element body is preferably annealed. Annealing is a process for re-oxidizing the dielectric layer, and thereby the IR life (insulation resistance life) can be remarkably increased, so that the reliability is improved.

The oxygen partial pressure in the annealing atmosphere is preferably 10 ⁻⁹ to 10 ⁻⁵ MPa. When the oxygen partial pressure is less than the above range, it is difficult to re-oxidize the dielectric layer, and when it exceeds the above range, oxidation of the internal electrode layer tends to proceed.

  The holding temperature at the time of annealing is preferably 1100 ° C. or less, and particularly preferably 1000 to 1100 ° C. When the holding temperature is lower than the above range, the dielectric layer is not sufficiently oxidized, so that the IR is low and the IR life tends to be short. On the other hand, if the holding temperature exceeds the above range, not only the internal electrode layer is oxidized and the capacity is lowered, but the internal electrode layer reacts with the dielectric substrate, the capacity temperature characteristic is deteriorated, the IR is lowered, the IR Life is likely to decrease. Note that annealing may be composed of only a temperature raising process and a temperature lowering process. That is, the temperature holding time may be zero. In this case, the holding temperature is synonymous with the maximum temperature.

As other annealing conditions, the temperature holding time is preferably 0 to 20 hours, and the cooling rate during annealing is preferably 50 to 500 ° C./hour. Further, as the annealing atmosphere gas, for example, humidified N ₂ gas or the like is preferably used.

In the above-described binder removal processing, firing and annealing, for example, a wetter or the like may be used to wet the N ₂ gas or mixed gas. In this case, the water temperature is preferably about 5 to 75 ° C.

  The binder removal treatment, firing and annealing may be performed continuously or independently.

  The capacitor element main body obtained as described above is subjected to end face polishing, for example, by barrel polishing or sand blasting, and the external electrode paste is applied and fired to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

  The multilayer ceramic capacitor of this embodiment manufactured in this way is mounted on a printed circuit board or the like by soldering or the like and used for various electronic devices.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, a multilayer ceramic capacitor is exemplified as an electronic component to which the dielectric ceramic composition according to the present invention is applied. However, as an electronic component to which the dielectric ceramic composition according to the present invention is applied, a multilayer ceramic capacitor is used. The present invention is not limited to a capacitor, and any capacitor may be used as long as it has a dielectric layer having the above configuration.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
First, BaTiO ₃ powder was prepared as a raw material for ABO ₃ , and ZrO ₂ , Y ₂ O ₃ , MgCO ₃ , MnCO ₃ and (Ba, Ca) SiO ₃ were prepared as raw materials for subcomponents. Incidentally, MgCO _3, after firing, and thus included in the dielectric ceramic composition as Mg-Zr-O solid solution or MgO.

Next, raw materials other than the ABO ₃ raw material prepared above were calcined under the conditions of calcining temperature: 1200 to 1350 ° C. and holding time: 2 hours, and the temperature lowering rate after the holding time at the calcining temperature was elapsed. It cooled as 100-400 degreeC / hour, and obtained the raw material powder (calcination raw material) after calcination. This calcined raw material and ABO ₃ raw material were wet-ground by a ball mill for 24 hours and dried to obtain a dielectric raw material.

In addition, the addition amount of each subcomponent is 3 mol of ZrO ₂ , ₂ mol of Y ₂ O ₃ , 2 mol of MgO with respect to 100 mol of BaTiO ₃ as the main component in the dielectric ceramic composition after firing, MnO was 0.3 mol and (Ba, Ca) SiO ₃ was 3 mol.

  Next, the obtained dielectric material: 100 parts by weight, polyvinyl butyral resin: 10 parts by weight, dioctyl phthalate (DOP) as a plasticizer: 5 parts by weight, and alcohol as a solvent: 100 parts by weight with a ball mill The mixture was made into a paste to obtain a dielectric layer paste.

  In addition to the above, Ni particles: 44.6 parts by weight, terpineol: 52 parts by weight, ethyl cellulose: 3 parts by weight, and benzotriazole: 0.4 parts by weight are kneaded with three rolls to obtain a slurry. To prepare an internal electrode layer paste.

  And the green sheet was formed on PET film using the dielectric layer paste produced above. Next, the electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, and then the sheet was peeled off from the PET film to produce a green sheet having the electrode layer. Next, a plurality of green sheets having electrode layers were laminated and pressure-bonded to obtain a green laminated body, and the green laminated body was cut into a predetermined size to obtain a green chip.

  Next, the obtained green chip was subjected to binder removal treatment, firing and annealing under the following conditions to obtain a sintered body serving as an element body.

  The binder removal treatment conditions were temperature rising rate: 25 ° C./hour, holding temperature: 260 ° C., temperature holding time: 8 hours, and atmosphere: in the air.

Firing was performed at a heating rate of 200 ° C./hour, a holding temperature of 1250 ° C., and a holding time of 2 hours. The temperature decreasing rate was the same as the temperature increasing rate. The atmospheric gas was a humidified N ₂ + H ₂ mixed gas (hydrogen concentration 1.0%), and the oxygen partial pressure was 10 ⁻¹² MPa.

The annealing conditions were: temperature rising rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, temperature falling rate: 200 ° C./hour, atmospheric gas: humidified N ₂ gas (oxygen partial pressure: 10 ⁻⁷ MPa). A wetter was used for humidifying the atmospheric gas during firing and annealing.

  Next, the end surface of the obtained sintered body was polished by sand blasting, and then a Cu paste was applied as an external electrode and baked to obtain a multilayer ceramic capacitor sample shown in FIG. The size of the obtained capacitor sample is 3.2 mm × 1.6 mm × 0.6 mm, the thickness of the dielectric layer is 10 μm, the thickness of the internal electrode layer is 1.5 μm, and the dielectric layer sandwiched between the internal electrode layers is The number was 4.

  For each of the obtained capacitor samples, the Zr content ratio (Zr1) in the diffusion region and the Zr content ratio (Zr2) in the crystal grain boundary were measured by the following methods. Next, the high temperature load life and DC bias characteristics were measured by the following methods. Since Zr0 is clearly smaller than Zr1 and Zr2, it was not measured.

Measurement of Zr1 and Zr2 First, the obtained capacitor sample was mechanically polished to a thickness of about 40 μm, then dimple processed to a thickness of about 10 μm, and then super-irradiated by Ar ion milling (PIPS). Processed into flakes. Twenty particles randomly extracted by STEM were observed on this ultrathin piece, and point analysis was performed by EDS at the grain boundary near the outer edge of each dielectric particle. The measured characteristic X-rays were quantitatively analyzed, the content ratio of Y and Zr was calculated, and the maximum content ratio of Y at the crystal grain boundary was calculated as Rmax. Moreover, the content ratio (Zr2) of Zr in the crystal grain boundary was calculated.

  Next, the mapping image of Y of the particles was subjected to image processing so that a region where the Y content was 50% or more of Rmax was a diffusion region and a region where less than 50% of Rmax was a central region. .

  Further, in the diffusion region, point analysis was performed by EDS attached to the STEM. The measured characteristic X-ray was quantitatively analyzed, and the content ratio (Zr1) of Zr in the diffusion region was calculated. The results are shown in Table 1.

The high temperature load life of the capacitor sample was evaluated by holding a DC voltage applied at 200 ° C. under an electric field of 20 V / μm and measuring the life time. In this example, the time from the start of application until the insulation resistance drops by an order of magnitude was defined as the breakdown time, and the mean failure time (MTTF) calculated by performing Weibull analysis was defined as the lifetime. Further, this high temperature load life was carried out for 10 capacitor samples. In this example, 10 hours or longer was considered good. The results are shown in Table 1.

A DC bias characteristic capacitor sample is held at 25 ° C. in an applied DC voltage under an electric field of 8 V / μm, and a digital LCR meter (YHP 4284A) has a frequency of 1 kHz and an input signal level (measurement voltage). ) The capacitance was measured under the condition of 1 Vrms, and the rate of change with respect to the capacitance at a reference temperature of 25 ° C. was calculated. In this example, -30% or more was considered good. The results are shown in Table 1.

  From Table 1, when the value of Zr1 / Zr2 is within the range of the present invention (sample numbers 2 and 3), good DC bias characteristics can be obtained while improving the reliability.

Example 2
Except that the value of Zr1 / Zr2 was 2.0, and the ratio of the number of dielectric particles 20 having a value of Zr1 / Zr2 within the scope of the present invention was the ratio shown in Table 2, the same as in Example 1, A capacitor sample was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

  From Table 2, when the number ratio of the dielectric particles satisfying the above relationship is within the range of the present invention (Sample Nos. 7 to 10), good DC bias characteristics can be obtained while improving the reliability. Can do.

Example 3
A capacitor sample was produced in the same manner as in Example 1 except that the calcining temperature and the temperature lowering rate under the calcining conditions were changed to those shown in Table 3, and the same evaluation as in Example 1 was performed. The results are shown in Table 3. Note that sample number 12 is the same as sample number 2 in Table 1, sample number 14 is the same as sample number 3 in Table 1, and sample number 15 is the same as sample number 1 in Table 1.

  From Table 3, it was confirmed that by changing the calcining temperature and the temperature lowering rate, Zr1 and Zr2 were changed and the value of Zr1 / Zr2 could be controlled. Moreover, it has been confirmed that the value of Zr1 / Zr2 can be easily within the range of the present invention by setting the temperature lowering rate to 200 ° C./hour or more.

Example 4
A capacitor sample was prepared in the same manner as in Example 1 except that only the combination of oxides shown in Table 4 was calcined and the calcining conditions were as shown in Table 4. Evaluation similar to Example 1 was performed. went. The results are shown in Table 4. In addition, with respect to 100 mol of BaTiO ₃ , the content of ZrO ₂ was 3 mol, the content of MgO was 2 mol, the content of Y ₂ O ₃ was 2 mol, and the content of SiO ₂ was 3 mol.

  From Table 4, the combination to be calcined is an oxide of Zr and an oxide of Mg, and the temperature lowering rate at the time of calcining is within the range of the present invention (sample number 24), reliability is improved, and It was confirmed that the DC bias characteristics can be improved.

  On the other hand, when a combination other than the combination of the oxide of Zr and the oxide of Mg is selected as the combination to be calcined (sample numbers 25 to 30), the reliability is not improved regardless of the temperature lowering rate at the time of calcining, It was confirmed that the DC bias characteristics also deteriorated. In addition, even when a combination of Zr oxide and Mg oxide is selected as the calcination combination, when the temperature drop rate during calcination is outside the scope of the present invention (Sample No. 23), It was confirmed that the reliability was not improved and the DC bias characteristics were also deteriorated.

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Capacitor element body 2 ... Dielectric layer 20 ... Dielectric particle 20a ... Central region 20b ... Diffusion region 21 ... Crystal grain boundary 22 ... Triple point 3 ... Internal electrode layer 4 ... External electrode

Claims (7)

A compound represented by the general formula ABO ₃ (A is Ba alone or at least one selected from Ba and Ca and Sr, and B is Ti);
An oxide of Zr;
R element oxide (wherein R element is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) And)
A dielectric porcelain composition containing an oxide of Mg,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary existing between two adjacent dielectric particles;
The maximum value of the content ratio of the R element in the crystal grain boundary is Rmax, the region in which the content ratio of the R element in the dielectric particles is 50% or more of Rmax is a diffusion region, and the diffusion in the dielectric particles The area other than the area is the central area,
When the content ratio of Zr in the central region is Zr0, the content ratio of Zr in the diffusion region is Zr1, and the content ratio of Zr in the crystal grain boundary is Zr2, Zr1>Zr2> Zr0 and Zr1 / Zr2 ≧ 1.5 Satisfied with a relationship
Ratio of dielectric particles satisfying the relationship in the number ratio state, and are more than 50% of the whole dielectric particles,
The dielectric ceramic composition characterized that you have exist Mg-Zr-O solid solution in the dielectric ceramic composition after firing. When the Mg content in the central region is Mg0, the Mg content in the diffusion region is Mg1, and the Mg content in the crystal grain boundary is Mg2, the relationship of Mg2> Mg1> Mg0 is satisfied. The dielectric ceramic composition according to claim 1. The dielectric ceramic composition according to claim 1 or 2 , wherein the dielectric ceramic composition contains an oxide of at least one element selected from Mn, Cr, Co, Fe, and Cu. The dielectric ceramic composition according to any one of claims 1 to 3, wherein the dielectric ceramic composition contains an oxide containing Si. Wherein for the compound 100 moles, the oxide of Zr is in Zr terms of element dielectric ceramic composition according to any one of claims 1-4 contained 0.5 mol or more. A compound represented by the general formula ABO ₃ (A is Ba alone or at least one selected from Ba and Ca and Sr, and B is Ti);
An oxide of Zr;
R element oxide (wherein R element is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) And)
A method for producing a dielectric ceramic composition containing an oxide of Mg,
Calcining the raw material of the Zr oxide and the raw material of the Mg oxide to obtain a post-reaction raw material containing an Mg—Zr—O solid solution;
Adding a raw material of the compound to the post-reaction raw material to obtain a dielectric raw material;
Firing the dielectric material, and
In the step of obtaining the post-reaction raw material, the calcining temperature is 900 to 1350 ° C., and the temperature lowering rate after calcining is 200 ° C./hour or more. The raw material for the Zr oxide is ZrO. ₂ The raw material for the Mg oxide is MgCO. ₃ The method for producing a dielectric ceramic composition according to claim 6.

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