DE10331036B4 - PZT (lead zirconate titanate) compositions which are sinterable at low temperatures and piezoelectric ceramic devices made therefrom - Google Patents

Abstract

Piezoelectric ceramic composition containing a ceramic material of the general formula [(Pb _1-mnp Sr _m Ba _n Cd _p ) (Zr _x Ti _{1 -x} ) _1-k (Bi _a Mn _b ) _k ] O ₃ + y Bi ₂ O ₃ + z LiF or MgF ₂ and wherein m, n, p, x, a, b and k, the subsequent values in the range of 0.00 ≤ m <0.15; 0.00 ≤ n <0.15; 0.00 <(m + n) <0.21; 0.00 <p <0.04; 0.50 ≤ x <0.56; 0.00 <a ≤ 1.00; 0.00 <b ≤ 1.00 and 0.00 <k <0.04
and y and z are in the range of 0.001 ≦ y ≦ 1.0 parts by weight and 0.001 ≦ z ≦ 1.0 parts by weight each based on 100 parts by weight of the ceramic material

Description

The The present invention relates to lead zirconate titanate (PZT) compositions, which are sinterable at low temperature and their use for piezoelectric Ceramic devices. The invention relates in particular to low-loss Piezoelectric ceramics that are at temperatures below of 1050 ° C are sinterable, and above in addition, together with a silver (Ag) electrode at a temperature of below 940 ° C can be sintered, and piezoelectric ceramic devices for the PZT compositions be used.

The Number of publications, the multilayer piezoelectric ceramic devices, such as Piezotransformatoren and Piezo triggers, is in the recent times increased strongly. However, the known multilayer piezoceramic devices had to from the material lead-zirconate-titanate (PZT) because of the high sintering temperature of the PZT material together with platinum (Pt), palladium (Pd) or silver-palladium paste be sintered. The high cost of the inner electrode limited the general use of the multilayer piezoelectric device one. That's why big ones got Made efforts to develop a PZT material, at low temperature, in particular below 962 ° C, i. the Melting point of silver, can be sintered.

In the continuous application, as is the case with the piezoelectric ceramic transformer, to achieve high efficiency, it is necessary to use a low-loss hard piezoceramic material having a high piezoelectric module d _ij , a high electromechanical coupling coefficient k _p , and a high dielectric constant , However, the reduction of the sintering temperature without impairing the piezoelectric property on the hard piezoceramic is associated with great difficulty. For accelerating the compression at a low temperature, the sintering temperature of the PZT material when sintered in the melt can be reduced simply by adding a glass frit having a low melting point. However, this is problematic in that it can change a piezo parameter in this method.

U.S. Patent Application No. 5,792,379 describes a PZT ceramic composition whose sintering temperature is below 900 ° C and which can be co-sintered with Ag as the internal electrode material. By using the sintering assistant selected from the group consisting of B ₂ O ₃ , Bi ₂ O ₃ , MeO (Me is a metal selected from the group consisting of Ca, Sr, Ba and Zn) and CuO, the sintering temperature became reduced. However, the comparison with a hard piezoceramic shows that the reduction in the sintering temperature whose k _p (electromechanical coupling coefficient) is greater than 0.60 reduces the k _p to a value of 0.55 or less.

U.S. Patent Application No. 5,433,917 discloses a PZT composition containing a eutectic mixture of CuO and an alkaline earth metal oxide having a low sintering temperature of about 1000 ° C. In addition to the dielectric constant and the dielectric loss, however, other piezo parameters are not described. Gui et al. describe a method in which the sintering temperature of PZT can be reduced by using small amounts of B ₂ O ₃ , Bi ₂ O ₃ and CdO.

at These known from the prior art PZT compositions but is problematic that the sintering temperature is still too high, to perform sintering together with the silver electrode.

at the known embodiments serves the glaze mass, which has a low melting point, although as a sintering aid, but all the elements in this glaze mass, such as. Boron can while the sintering process is not replaced because of the crystal lattice structure so that these elements after sintering along the grain boundary remain on the glass, reducing the piezoelectric properties be worsened.

1 Fig. 12 is a perspective view of a piezoelectric ceramic transformer which is an embodiment of the piezoelectric device according to the present invention;

2 FIG. 12 is a diagram showing the frequency characteristics of the output voltage of the piezoelectric ceramic transformer which is an embodiment of the piezoelectric device according to the present invention; FIG.

3 shows a diagram showing the frequency characteristics of the external resistance (continuity the state) (100 MOhm) and 200 kOhm of the piezoelectric ceramic transformer, which is one embodiment of the piezoelectric device according to the present invention, and

4 FIG. 12 is a graph showing the energy characteristics of output current and output voltage of the piezoelectric ceramic transformer which is an embodiment of the piezoelectric device according to the present invention.

In 1 where I is the input section O is the output section and P is the polarization.

following become the preferred embodiments described.

Around to solve the above problems, It is an object of the present invention, piezoelectric To provide ceramic compositions which are low in temperature with a low dielectric loss and high piezoelectric Parameters can be subjected to the sintering process.

A Another object of the present invention is to provide piezoelectric To provide ceramic compositions by common Sintering a piezoelectric ceramic with pure silver below the melting point of silver (Ag) of 962 ° C is available.

A Another object of the present invention is to provide piezoelectric To provide ceramic devices used in continuous applications, as in the multilayer piezoelectric ceramic transformer, are suitable as a multilayer piezoelectric trigger.

In order to achieve the above objects, the present invention provides a piezoelectric ceramic composition comprising a ceramic material having the general formula [(Pb _1-mnp Sr _m Ba _n Cd _p ) (Zr _x Ti _1-x ) _1-k (Bi _a Mn _b ) _k ] O ₃ + 0.001 to 1.0 parts by weight Bi ₂ O ₃ + 0.001 to 1.0 part by weight of LiF or MgF ₂ contains
wherein m, n, p, x, a, b and k, the subsequent values in the range of 0.00 ≤ m <0.15; 0.00 ≤ n <0.15; 0.00 <(m + n) <0.21; 0.00 <p <0.04; 0.50 ≤ x <0.56; 0.00 <a ≤ 1.00; 0.00 <b ≤ 1.00 and 0.00 <k <0.04
exhibit.

following The present invention will be described in detail.

The piezoelectric ceramic compositions contain a ceramic material as an essential element [(Pb _1-mnp Sr _m Ba _n Cd _p ) (Zr _x Ti _1-x ) _1-k (Bi _a Mn _b ) _k ] O ₃ + 0.001 to 1.0 parts by weight Bi ₂ O ₃ + 0.001 to 1.0 parts by weight of LiF or _MgF2 and
wherein m, n, p, x, a, b and k are the following values in the range of 0.00 ≦ m <0.15; 0.00 ≤ n <0.15; 0.00 <(m + n) <0.21; 0.00 <p <0.04; 0.50 ≤ x <0.56; 0.00 <a ≤ 1.00; 0.00 <b ≤ 1.00 and 0.00 <k <0.04
exhibit.

In the above described ceramic, the lead zirconate titanate (PZT) solid alloy was alloyed with strontium, barium, cadmium, bismuth, lithium. In order to reduce the sintering temperature, reactive Cd and Bi are added, and the piezoelectric parameters do not deteriorate. Bi ³⁺ replaces Zr ⁴⁺ , or Ti ⁴⁺ and the charge neutrality required by the replacement of the aliovalent ions is maintained by creating oxygen-free sites that increase the diffusion process during the sintering process and thereby reduce the effective sintering temperature. Cd ²⁺ ions replace Pb ²⁺ ions in this system and their high reactivity accelerates the diffusion process during the sintering process and effectively lowers the sintering temperature. The amount of Cd, p, is limited to 0 <p <0.04. With a lot outside this range, the electromechanical coupling coefficient, k _p and the piezo module, d ₃₃ , are reduced to an inexecutable level.

Bi is added in conjunction with manganese as (Bi _a Mn _b ) as shown in the above formula. Manganese is added to increase the mechanical quality factor Q _m and to control the yield of the sintered elements. The relative amounts of Bi and manganese, a and b, are in a range of 0 <(a or b) ≦ 1 and are used to satisfy the following equation 3a + 4b = 4. This is the case if, for example, a takes the values 1, 2/3, 1/2 or 1/3 or b the values 1/4, 1/2, 5/8 or ¾.

Given the place in the matrix, the Bi ³⁺ or Mn ⁴⁺ ions in the Ti ⁴⁺ and Zr ⁴⁺ sites in An This assumption leads to excess Bi ³⁺ or Mn ⁴⁺ ions, in an amount of k (a / 4) moles for each mole of the matrix, when Bi ³⁺ and Mn ⁴⁺ ions are replaced by Zr ⁴⁺ - And Ti ⁴⁺ ions are replaced. The excess Bi ³⁺ or Mn ⁴⁺ ions which are not contained in the liquid phase of the PZT matrix form are compressed during the sintering process as auxiliaries. The maximum amount of (Bi _a Mn _b ), k is limited to 0 <k <0.04. Beyond this value, the parameters k _p and d ₃₃ decrease drastically.

sr or Ba are added, to improve densification with a high dielectric constant, without adversely affecting the piezoelectric para meters. The maximum amount of Sr or Ba that can be used to replace Pb is approximately 15 mol% in the PZT when added alone. If they are together added maximum amount of (Sr + Ba) can be increased to 18-20 mol% and therefore a much higher one permittivity reachable. additionally the use of the mixture shows a better sintering behavior than it with the use of individual ions in the same amount in Atomic percent is achieved. The amount of Sr or Ba, m or of n is limited to 0.0 <(m or N) <0.15 with 0 <(m + n) <0.21. Higher values increase the sintering temperature too high.

The piezoelectric compositions according to the present invention contain from 0.001 to 1 part by weight of Bi ₂ O ₃ in order to improve sintering or mechanical quality factor.

Further additives consist of mixtures of fluorine compounds, such as LiF and MgF ₂ . Fluorine improves the piezoelectric properties at a high electric field and increases the dielectric constant. For this purpose, a fluorine compound is added to the composition of the present invention. The amount of F in the form of LiF or MgF ₂ is limited to 0.01 <z <1.0 in weight%.

It is preferable that the piezoelectric compositions contain 0.001 to 0.50 parts by weight of MnO _{2 in} order to improve sinterability or the mechanical quality factor.

With The present invention will be a piezoelectric ceramic device provided by sintering at a temperature below of 1075 ° C of the piezoelectric ceramic composition according to the above said formula is produced.

With The present invention also provides a multilayer piezoelectric Ceramic device provided by co-sintering a piezoelectric ceramic composition and an inner electrode silver at a temperature below 960 ° C is available.

With The present invention also provides the multilayer piezoelectric Ceramic device provided by co-sintering a piezoelectric ceramic composition and an inner electrode available in silver-palladium is. It is preferable that the amount of palladium (Pd) in terms of 100 parts by weight of silver and palladium from 0.001 to 20 parts by weight enough.

With Moreover, according to the present invention, the piezoelectric Ceramic device provided by co-sintering a piezoelectric ceramic composition and an inner electrode Silver is available at a temperature below 960 ° C.

In addition, will with the present invention also a multilayer piezoelectric Ceramic device provided by co-sintering a piezoelectric ceramic composition and an inner electrode of silver at a temperature below 1050 ° C is available and the a plurality of multi-layered sections and single-layered ones Has sections. It is preferred that the amount of palladium (Pd) with respect to 100 parts by weight of silver and palladium of 0.001 to 20 parts by weight is enough.

The The present invention is accomplished by the following embodiments the piezoelectric ceramic compositions and the piezoelectric Ceramic transformer illustrated. The embodiments are used to explain the present invention without limiting it to these.

Examples

Example 1: Piezoelectric ceramic compositions

PbO, ZrO ₂ , TiO ₂ , SrCO, BaCO ₃ , CdO, Bi ₂ O ₃ , MnO ₂ and LiF or MgF ₂ were used as starting materials. These compounds are used according to the desired composition shown in Table 1, wherein m, n, p, x, a, b and k are the indices in the above-mentioned formula of the piezoelectric y is the amount in parts by weight of Bi ₂ O ₃ and z is the amount in parts by weight of the added fluorine compound.

The Materials were in the indicated amounts with deionized water wet mixed in a grinder for 2 hours, then the greasy product obtained was applied under application of a Vacuum filtered off. The filtered cake was oven dried at 120 ° C and then over 2 hours fired at 700-875 ° C. The fired material became average in a grinder Particle size of about 0.8 microns rubbed.

The heavily crushed material was in powder form in a 10% PVA solution taken up, dried and then granulated. It was the PVA content about 2% by weight of the powder.

From these granules, disc-shaped blanks having a diameter of 25 mm and a thickness of about 2.5 mm were produced under a pressure of 1,000 kg / cm ² . These blanks were subjected to sintering at 920-1000 ° C for 2 hours. Paste-form Ag was printed on both sides of the sintered slices and fired at 700-770 ° C for 15 minutes.

The Electrode disks were at 3-4 kV / mm in silicone oil bath at 120-140 ° C for 15 minutes polarized. The dielectric constant and the extent of Loss of non-conductive properties were in continuous operation at 1 kHz measured and the remaining charge with an input level measured or determined by 1 Vrms.

The piezoelectric module, d ₃₃ , was measured with a Berlincourt d ₃₃ measuring instrument. The planar coupling coefficient, k _p and the mechanical quality factor, Q _m , were calculated using the following equations 1 / k p 2 = 0.395fr / (f a - f r + 0.574 Q m = 1/2 πf r Z r C 0 (1 - (f r / f a ) 2 ) wherein f _{r is} the resonant frequency, f _a, the anti-resonant frequency, Z _r the resonant resistance, which was measured using an impedance / gain phase analyzer, and C _0, the capacitance measured in continuous operation and to which the remaining charge was determined mean.

The Compositions marked with an asterisk * in Table 1 are, are comparative samples and are outside the range of the present Invention.

The Characteristics of samples subjected to sintering at 1050 ° C, 965 ° C and 950 ° C, are shown in Table 2. As the results show, excellent piezoelectric parameters with the samples sintered at 1050 ° C were achieved, and these are at a sintering temperature of 950 ° C maintained.

When the amount of Cd, p, is 0.04 (sample 4), the electromechanical coupling coefficient, k _p , decreases drastically. When the total amount of (Ba + Sr) is 22 mol% (Samples # 1 and # 2), the k _p value greatly decreases even at these sintering temperatures, particularly because the spreading ability of Ba and Sr Ion is slowed down when compared to the values of Pb.

Samples # 11 and # 12 show that a fluorour compound can be added up to 1% by weight without affecting electromechanical coupling. MgF ₂ can be used, but the data obtained for samples containing MgF ₂ are significantly inferior to the samples containing LiF.

Different properties can be achieved by changing the Zr / Ti ratio. Low temperature starting compositions in which the Zr / Ti ratio is changed correspond to the present invention as shown in Table 3, wherein m, n, p, x, a, b and k are the indices of the above formula for the y is the amount in parts by weight of Bi ₂ O ₃ and with z the amount of fluorine compound is also given in parts by weight.

• y gibt in Gewichtsteilen die Menge an Bi₂O₃ an und
• z gibt in Gewichtsteilen die Menge an Fluorverbindung an.

Tabelle 2

Tabelle 3

• y gibt in Gewichtsteilen die Menge an Bi₂O₃ an und
• z gibt in Gewichtsteilen die Menge an Fluorverbindung an.

Tabelle 4

The compositions were sintered at 940 ° C. The properties of the prepared piezoelectric blank discs are shown in Table 4. All compositions sintered at 940 ° C were good and showed good piezoelectric properties; a small dielectric loss of 0.2-0.4%, a high dielectric constant of 1470 to 1850, a d ₃₃ of 310-396 and a mechanical quality factor Q _m of 610-730. By changing the Zr / Ti ratio, it was possible to change the temperature coefficient of the resonance frequency and the dielectric constant as shown in Samples # 61-64. By adding LiF, the dielectric constants could increase a deterioration of the temperature coefficient of the resonance frequency, as shown in samples # 63 and # 65. Such a low sintering temperature makes it possible to use pure Ag paste as internal electrodes in multi-layered piezoelectric ceramic components such as piezoelectric ceramic transformers and piezoelectric starters (actuators). High dielectric constants and the obtained temperature coefficients of resonant frequency achieved are advantageous for applications involving a resonant module, such as in a piezoelectric ceramic transformer. Table 1

• y indicates in parts by weight the amount of Bi ₂ O ₃ and
• z indicates in parts by weight the amount of fluorine compound.

Table 2

Table 3

• y indicates in parts by weight the amount of Bi ₂ O ₃ and
• z indicates in parts by weight the amount of fluorine compound.

Table 4

Example 2: Piezoelectric Ceramic transformer with an inner electrode made of pure silver

With the composition according to the present invention, a piezoelectric ceramic transformer was produced. 1 shows a sheet-like structure of the formed piezoelectric ceramic transformer. The input section has a multilayer structure in which each layer is polarized alternately up and down in the direction of the starches, as shown in the figure. The output section is formed by the single layer and polarized along the length of the transformer.

The manufacture of the multilayer piezoelectric ceramic transformer begins with the preparation of the sheet-like blank of the PZT material. Burned material was mixed in a ball mill for 6 hours with a standard solution consisting of polyvinyl butyral (PVB), dibutyl phthalate (DBP), tran (fish oil), methyl ethyl ketone (MEK) and toluene. The printed or embossed greasy material was defoamed under vacuum and made into 95 micron thick sticky tapes by applying the mass to a household film with a doctor blade. The sticky band-shaped blanks were cut into pieces measuring 150 mm × 150 mm with superimposed holes. Alternating patterns of the internal electrodes were printed on the sheet blanks with a pure Ag paste and dried in a continuous oven. The printed blanks were in register with each other lying holes in vacuum at 85 ° C hot stacked. The hot-laminated rod-shaped blanks were cut in various shapes to different blank shapes. Solvent, as well as the other organic products present in the blanks, were burned out at 260 ° C and then sintered at 940 ° C for 2 hours. External input and output electrodes served as shielding, printed with Ag paste and fired at 780 ° C. The polarization was carried out in the silicone oil bath at 130 ° C with polarization voltages of 450 VDC for the input section and 25 kVDC for the output section.

The dimensions of the piezoelectric ceramic transformer were 26.0 mm × 5.0 mm × 1.3 mm and had 16 internal electrodes with 15 piezo-active layers. The Ag paste slightly reacted with the PZT matrix formed from the composition of sample # 63 according to the present invention, with co-sintering being uniform at 940 ° C. The coating of the inner electrode with the Ag was excellent without any noticeable pores or exfoliation. Very small resonance resistance and excellent piezoelectric properties were obtained. The properties of the piezoelectric ceramic transformer are shown in Table 5. The energy distributions are in 2 shown. The measured conversion efficiency was greater than 93%.

Table 5

The Use of the starting materials at low temperature accordingly this invention is not applicable to the piezoelectric ceramic Limited transformers. It can be based on multi-layered starter (trigger), multi-layered Sensors, as well as bimorphic materials, as well as piezoelectric transducers be used with known individual layers.

As stated above are the piezoelectric ceramic compositions according to the present invention Invention with a low dielectric loss and high piezoelectric Parameters together with pure silver at low temperature, in particular the melting temperature of the silver of 962 ° C, simultaneously sinterable.

at the continuously performed Application, as in the piezoelectric ceramic transformer, when multilayer piezoelectric ceramic resolver, etc. is a piezoelectric Ceramic device required, and excellent conversion efficiency shows.

Claims (11)

Piezoelectric ceramic composition containing a ceramic material of the general formula [(Pb _1-mnp Sr _m Ba _n Cd _p ) (Zr _x Ti _{1 -x} ) _1-k (Bi _a Mn _b ) _k ] O ₃ + y Bi ₂ O ₃ + z LiF or MgF ₂ and wherein m, n, p, x, a, b and k, the subsequent values in the range of 0.00 ≤ m <0.15; 0.00 ≤ n <0.15; 0.00 <(m + n) <0.21; 0.00 <p <0.04; 0.50 ≤ x <0.56; 0.00 <a ≤ 1.00; Have 0.00 <b ≦ 1.00 and 0.00 <k <0.04, y and z in the range of 0.001 ≦ y ≦ 1.0 parts by weight and 0.001 ≦ z ≦ 1.0 parts by weight each based on 100 parts by weight of the ceramic material lie Piezoelectric ceramic compositions according to claim 1, characterized in that a and b satisfy equation 3a + 4b = 4. Piezoelectric ceramic compositions according to claim 1, characterized in that p and satisfy k p = k. Piezoelectric ceramic compositions according to claim 1, characterized in that it contains 0.001 to 0.50 parts by weight of MnO ₂ . Piezoelectric ceramic device containing a piezoelectric ceramics obtained by sintering a ceramic composition according to one of the claims 1 to 4 is available at a temperature below 1075 ° C, Multilayer piezoelectric ceramic device available by co-sintering a piezoelectric ceramic composition according to one of the claims 1 to 4 and an inner electrode made of silver at temperatures below of 960 ° C. Multilayer piezoelectric ceramic device available by co-sintering a piezoelectric ceramic composition according to one of the claims 1 to 4 and an inner electrode of silver-palladium. Multilayer piezoelectric ceramic device according to claim 7, characterized in that the amount of palladium (Pd) with respect to 100 parts by weight of silver and palladium of 0.001 to 20 parts by weight is sufficient. Piezoelectric ceramic device obtainable by co-sintering a piezoelectric ceramic composition according to one of the claims 1 to 4 and an inner electrode made of silver at temperatures below of 960 ° C, the multi-layered and single-layered sections. Piezoelectric ceramic device obtainable by co-sintering a piezoelectric ceramic composition according to one of the claims 1 to 4 and an inner electrode of silver-palladium at temperatures below 1050 ° C, the multi-layered and single-layered sections. Piezoelectric ceramic device according to claim 10, characterized in that the Amount of palladium (Pd) with respect to 100 parts by weight of silver and palladium ranges from 0.001 to 20 parts by weight.