JPS6217368B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a CaTiO ₃ --SrTiO ₃ semiconductor ceramic capacitor body having a high dielectric constant and a very small temperature change rate. Magnetic capacitors have traditionally been used in the trimmers of electronic watches, but the relative permittivity of these capacitors is
There is a strong demand for a material with a large dielectric constant of about 100 to 200. Many semiconductor capacitors that have been developed in recent years are BaTiO ₃ -based and SrTiO ₃ -based with large capacities, but their dielectric constants change with temperature at 20°C and -25°C to +85°C, respectively.
This value is 15 to 40%, ±8 to 15%, which is much larger than the ±5% required by watch trimmers. Also, for trimmers, it is necessary to make a hole in the center of the disc with a capacity of several tens to hundreds of pF, but when making a hole with a thickness of 0.5 mm of about 200 pF and a material with a dielectric constant of 10,000 or more. Its diameter must be 1 mm or less, which causes difficulty in drilling. Therefore, a value of the dielectric constant of about 1000 to 3500 is required, and the present invention satisfies the requirements for the dielectric constant and its rate of change with temperature. That is, the present invention uses CaO14 to 22 mol%, SrO28
In the SrTiO ₃ -CaTiO ₃ solid solution system with a composition of ~36 mol% and TiO ₂ 49.5-50.5 mol%, the phase at room temperature is the boundary region between cubic and tetragonal crystals, and in order to convert it into a semiconductor, At least one of Ta ₂ O ₅ and Nb ₂ O ₅ is added in an amount of 0.02 to 1.2 molar parts. In this case, there is no problem in adding it in the form of metal. Furthermore, in order to improve the dielectric loss, 0.2 to 1.1 mole parts of at least one of GeO ₂ and SiO ₂ is added as an accessory component to 100 mole parts of the basic composition. Alternatively, in order to improve the temperature change rate of the dielectric constant, 0.1 to 1.9 parts by mole of ZnO is added as a subcomponent to 100 parts by mole of the basic composition. Next, these compositions are fired in a neutral or reducing atmosphere to produce a semiconductor ceramic body. Thereafter, by processing in air, only the grain boundary layer is made into an insulator, which is then used as the element body of the capacitor. There are roughly two methods for making this insulator. One is Cu,
One method is to apply metals, oxides, and metal salts of Bi and Mn to the semiconductor surface and then thermally diffuse them in the air.One method is to apply no metal to the surface and heat-treat it in the air. By the above method, the apparent dielectric constant is 1000 to 3500, and its temperature change rate is (20℃ standard,
-25℃ to +85℃) ±1 to 5%, tan δ10 to 55×
10 ^-4 and a specific resistance of 10 ¹⁰ to 3×10 ¹² Ω-cm can be obtained. Next, the details of the present invention will be explained by giving examples. Example 1 Industrial raw materials CaCO ₃ , SrCO ₃ , TiO ₂ , Ta ₂ O ₅ ,
Nb ₂ O ₅ powder was mixed wet for 20 hours, and after drying, calcining was performed at 1200° C. for 2 hours to increase uniformity and to complete the reaction. Next, this was crushed for 20 hours, a polyvinyl alcohol aqueous solution was added as a binder, and the powder was crushed at a pressure of 800 kg/cm ² to a thickness of 0.5 mm and a diameter of 0.5 mm.
It was molded into a 5.0 mm disc. This was heat treated in air at 800℃ to remove the binder, and then
%H ₂ −97%N ₂ 3 at 1380° to 1440° in gas flow
I baked it for an hour. The element thus created is black and has a resistance of several ohms. It is a semiconductor with a resistivity of cm. Copper oxide dispersed in organic matter is applied to this surface per 1gr of element body.
1.0×10 ^-5 gr atoms (approximately per 30 mgr element)
0.03 mgr) and thermally diffused in air at 1100°C for 2 hours. A commercially available silver electrode was applied to this element body, and various properties were measured. The obtained results are shown in Tables 1 and 2.
Table 3 shows the results. Table 1 shows 50 mol % of TiO ₂ , 0.2 mol part of added Ta ₂ O ₅ and different amounts of CaO and SrO. CaTiO ₃ −SrTiO ₃ −Nb ₂ O ₅ ceramics are already known, but their dielectric constant is around 280, and their temperature coefficient is the lowest.
Approximately 650ppm (20℃ standard -25℃ to +85℃ is ±4.3
%), but the present invention achieves a minimum value of approximately ±2%, and here the characteristics of the grain boundary layer are exhibited. This is thought to be due to a combination of distortion in the grain boundary layer, impurity concentration effect, and diffused substance effect.
As is clear from Table 1, when CaO is 14 mol% or less (SrO is 36 mol% or more) and CaO is 22 mol% or more (SrO is 28 mol% or less), the temperature coefficient exceeds ±5%, which is not preferable. Table 2 shows CaO:SrO=18:
The amount of TiO ₂ was changed by 0.2 mole part of 32% Ta ₂ O ₅ . As is clear from the results, the amount of TiO ₂ is 49.5
If it is less than mol %, the dielectric constant will drop rapidly, which is undesirable. On the other hand, if it is more than 50.5 mol %, tan δ will become large, which is undesirable. Table 3 shows CaO18 mol%, SrO32
mol%, the amount of Ta ₂ O ₅ added at 50 mol% of TiO ₂ is 0
This is the result of changing up to ~1.5 mole part, and 1.2
If it is more than 0.02 molar part, the dielectric constant will drop rapidly, which is undesirable, and if it is less than 0.02 molar part, tan δ will be large, which is undesirable.

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[Table] Table 4 shows the results when part or all of Ta ₂ O ₅ was replaced with Nb ₂ O ₅ . This results in Ta ₂ O ₅ and
It can be seen that Nb ₂ O ₅ is almost the same. Example 2 GeO ₂ , SiO ₂ , and ZnO were added to 18 mol% CaO, 2 mol% SrO, 50 mol% TiO ₂ , and 0.2 mol part of Ta ₂ O ₅ , and after calcination, the binder was removed and the mixture was placed in a tube furnace. is. After removing the air in the furnace with a rotary pump, it was heated at 1370℃ to 1430℃ for 3 times while flowing _N2 gas.
The product was baked for a period of time, and the same steps as in Example 1 were carried out to measure the characteristics. Table 5 shows the results.

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[Table] GeO ₂ and SiO ₂ have almost the same effect, and have a characteristic that tan δ is improved, although the dielectric constant is slightly lower. There is no effect if the amount added is less than 0.2 mol part, and 1.2
If it is more than a molar part, the dielectric constant becomes less than 1000, which is not preferable. Regarding ZnO, if it is less than 0.1 mole part, it has no effect, and if it is more than 0.9 mole part, the tan δ will deteriorate rapidly, which is not preferable. ZnO is characterized by good temperature characteristics. Example 3 A composition containing 18 mol% of CaO, 2 mol% of SrO, 50 mol% of TiO ₂ and 0.2 mol of Ta ₂ O ₅ was calcined, then molded.
Binder out and 1% H ₂ − at 1380°~1420°C
Calcined in 99% _N2 gas for 3 hours. Oxides of Cu, Bi, and Mn are dispersed in organic matter, some are deposited with metal, and some are added in the form of oxalate to this semiconductor element, and the mixture is exposed to air at a temperature of 950℃ to 1350℃. It was diffused for 2 hours. The amount of Cu oxide applied is
The coating amount of Bi oxide was in the range of 0.005 mgr to 10 mgr, and the coating amount of Mn oxide was in the range of 0.003 mgr to 2.4 mgr per 30 mgr element body. The results are shown in Table 6. Set the diffusion temperature to 1100℃ for Cu, 1150℃ for Bi, and 1150℃ for Mn.
If the amount of Cu applied is 20 × 10 ^-4 gr atoms or more, tanδ will deteriorate, which is undesirable, and if Bi is 1.0 ×
If it is more than 10 ^-3 gr atoms, the tan δ will be bad, which is undesirable, and if Mn is more than 4.0×10 ^-4 gr atoms, the dielectric constant will be undesirable. It can be seen that the substances marked with M and S in the table are metals and oxalates, respectively, and have equivalent effects. The characteristics of each element are that Cu has a relatively high dielectric constant, Mn has good temperature characteristics, and Bi is in the middle. 2
By applying a combination of species or more, you can obtain the desired characteristics between them. Also, regarding the diffusion temperature
Cu, Bi, and Mn below 950℃, 1000℃, and 1000℃ are undesirable because their specific resistance is low.
At temperatures above 1250°C, 1300°C, and 1300°C, the dielectric constant becomes low, which is not preferable.

【table】

[Table] Example 4 A semiconductor element made in the same process as Example 3 was heat-treated in air for 2 hours without applying anything to the surface to make the grain boundaries an insulator. Apply electrodes,
Characteristics were measured. The results are shown in Table 7. If the treatment temperature is 1000° C. or lower, the specific resistance will be low and the tan δ will be high, which is undesirable, and if the treatment temperature is 1300° C. or higher, the dielectric constant will be low, which is undesirable.

[Table] In Tables 1 to 7 above, the relative permittivity and
taoδ is a value at 20°C and 1KHz, and the relative dielectric constant changes with temperature at 1KHz, showing a maximum rate of change between -25°C and +85°C with 20°C as a reference. Also, the specific resistance is DC per 1 mm.
This is the value when 100V is applied. Also, the * marked in the table number is reference data that is outside the scope of the present invention. As described above, according to the present invention, it is possible to obtain a semiconductor ceramic capacitor body having a high dielectric constant and a very small rate of temperature change.

Claims (1)

[Claims] 1 CaO 14-22 mol%, SrO 28-36 mol%,
At least one of Ta ₂ O ₅ and Nb ₂ O ₅ is added to 100 mol parts of a composition consisting of 49.5 to 50.5 mol % of TiO ₂ .
A semiconductor porcelain capacitor element body, characterized in that the main component is a composition to which 0.02 to 1.2 mole parts is added, which is fired in a neutral or reducing atmosphere to form a semiconductor porcelain, and then only the grain boundary layer of the semiconductor porcelain is made into an insulator. manufacturing method. 2. Less than 25 × 10 ^-4 gr atoms per 1 gr in semiconductor porcelain
The semiconductor according to claim 1, wherein only the grain boundary layer is made into an insulator by applying Cu metal, oxide, or metal salt and heat-treating at 950° to 1250°C in an air atmosphere. A method of manufacturing a ceramic capacitor body. 3 Add Bi metal, oxide, or metal salt of 10×10 ^-3 gr atoms or less per gram to the fired semiconductor porcelain, and heat-treat it at 1000° to 1300°C in an air atmosphere to remove only the grain boundary layer. A method of manufacturing a semiconductor ceramic capacitor element according to claim 1, characterized in that the element is made into an insulator. 4 Less than 4.0×10 ^-4 gr atoms per 1 gr in semiconductor porcelain
Claim 1, characterized in that a metal, oxide or metal salt of Mn is applied, and heat treatment is performed at 1000° to 1300°C in an air atmosphere to convert only the grain boundary layer into an insulator. A method for manufacturing a semiconductor ceramic capacitor body. 5 At least two or more of Cu, Bi, or Mn metals, oxides, or metal salts with an amount of 10 × 10 ^-3 gr atoms or less per gram are added to the fired semiconductor porcelain, and heated at 1000° to 1300°C in an air atmosphere. 2. The method of manufacturing a semiconductor ceramic capacitor element according to claim 1, wherein only the grain boundary layer is made into an insulator by heat treatment. 6 The semiconductor porcelain is further placed in an air atmosphere.
A method for manufacturing a semiconductor ceramic capacitor element according to claim 1, characterized in that the grain boundary layer is made into an insulator by heat treatment at 1000° to 1300°C. 7 CaO14-22 mol%, SrO28-36 mol%,
0.02 of at least one of Ta ₂ O ₅ and Nb ₂ O ₅ to 100 mol parts of a composition consisting of 49.5 to 50.5 mol % of TiO ₂
~1.2 mol parts, and further added 0.2 to 1.2 mol parts of at least one of GeO ₂ and SiO ₂ ,
A method for manufacturing a semiconductor ceramic capacitor body, which comprises firing in a neutral or reducing atmosphere to form a semiconductor ceramic, and then converting only the grain boundary layer of the semiconductor ceramic into an insulator. 8 CaO14-22 mol%, SrO28-36 mol%,
At least one of Ta ₂ O ₅ and Nb ₂ O ₅ is added to 100 mol parts of a composition consisting of 49.5 to 50.5 mol % of TiO ₂ .
A composition containing 0.02 to 1.2 mole parts and further 0.1 to 1.9 mole parts of ZnO is fired in a neutral or reducing atmosphere to produce semiconductor porcelain, and then only the grain boundary layer thereof is made into an insulator. A method for manufacturing a semiconductor ceramic capacitor body.