KR100497644B1 - Soft piezoelectric ceramic composition and piezoelectric devices using the same - Google Patents

Abstract

The present invention relates to a soft piezoelectric ceramic composition and a piezoelectric ceramic device using the same, and more particularly, [(Pb _1-mn Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _{1 -x} ) _1-ab Ni _a W _b ] O ₃ , wherein m, n, x, y, a and b are 0.00 ≦ m ≦ 0.18 as molar ratio, 0.00 ≦ n ≦ 0.18, and 0.00 ≦ (m + n ) ≤ 0.21, 0.40 ≤ x ≤ 0.60, 0.000 <y ≤ 0.04, 0.00 ≤ a ≤ 0.02, and 0.00 <b ≤ 0.02. The present invention relates to a soft piezoelectric ceramic composition and a piezoelectric ceramic device using the same.

The soft piezoelectric ceramic composition of the present invention has a high piezoelectric constant and an electro-mechanical coupling coefficient, and is capable of co-sintering with silver (Ag) electrodes, thereby providing silver (Ag). It is possible to manufacture a piezoelectric ceramic device having a pure silver internal electrode which can reduce the cost of the electrode compared to the palladium (Pd) internal electrode.

Description

Flexible piezoelectric ceramic composition and piezoelectric ceramic device using the same {SOFT PIEZOELECTRIC CERAMIC COMPOSITION AND PIEZOELECTRIC DEVICES USING THE SAME}

The present invention relates to a soft piezoelectric ceramic composition and a piezoelectric ceramic device using the same. More particularly, the present invention relates to a soft piezoelectric ceramic composition having a high piezoelectric parameter and capable of co-sintering with silver (Ag) electrodes at a reduced temperature. soft) piezoelectric ceramic composition and a piezoelectric ceramic device using the same.

Recently, piezoelectric actuators have been successfully applied for valve control of fuel injection systems in diesel engines, opening the way for large-scale commercial applications of multilayer piezoelectric actuators. Also, in this case, it is usually necessary to have a high piezoelectric constant Soft lead zirconium titanate (PZT) materials are applied to piezoelectric actuators. On the other hand, monolithic multilayer structures are chosen to achieve sufficient displacement at low input voltages in automobiles.

However, in the production of piezoelectric ceramic devices such as multilayer piezoelectric actuators using soft PZT (Pb (Zr Ti) O ₃ ) materials, high silver (Ag) -palladium (Pd) is used as an internal electrode due to the high co-sintering temperature. Or platinum (Pt) alloys were commonly used. The amount of palladium (Pd), when sintered at 1150 to 1300 ° C., depends on the sintering temperature within the range of 20 to 70 wt%. Therefore, many technical efforts have been made to lower the sintering temperature of piezoelectric ceramics below the melting point of silver (Ag) in order to reduce the cost of the internal electrode in the multilayer piezoelectric actuator.

Soft piezoelectric ceramic materials have the following typical characteristics.

1) high piezoelectric constant,

2) high electro-mechanical coupling coefficient (Kp),

3) high dielectric constant,

4) high dielectric loss

5) low mechanical quality factor (Qm) and

6) Low coercive field and high residual polarization

In materials based on PZT (Pb (Zr Ti) O ₃ ), the properties of the soft piezoelectric ceramic materials have high valence of Zr ⁴⁺ or Ti ⁴⁺ . It can obtain by substituting by ^{Nb5 +} , Ta5 ⁺ , ^{W6 +} etc., or substituting ^{Pb2 +} by La3 ⁺ . However, conventional soft PZT materials have a sintering temperature of 1150 to 1200 ° C (Ref. 1). H. Zheng et. al., "Effects of Octahedral Tilting on the Piezoelectric Properties of Strontium / Barium / Niobium-doped Soft Lead Zirconate Titanate Ceramics", J. of Am. Ceram Soc. 85 [9], 2337 (2002), 2) US Patent 5,423, 995), expensive silver (Ag) -palladium (Pd) alloys used to make piezoelectric ceramic devices such as multilayer actuators by co-sintering green sheets with internal electrodes. There is a problem that must be done.

The sintering temperature of PZT material is diboride (B ₂ O ₃ ), vanadium pentoxide (V ₂ O ₅ ), bismuth oxide (Bi ₂ O ₃ ), copper oxide (CuO) to form a liquid phase that enhances densification at a lowered temperature It can be reduced by adding a sintering aid such as). (Reference) 1) US Patent 5,423,995, 2) US Patent 5,433,917, 3) US Patent No. 5,792,379, 4) K. Murakami et. al. "Morphotropic Phase Boundary and Microstructure of Low-Temperature sintered PZT ceramics with BiFeO ₃ and Ba (Cu _0.5 W _0.5 ) O ₃ ", Proceedings of the Ninth IEEE International Symposium on Applications of Ferroelectrics 5) X. Wang et.al., " The Mechanism of Low Temperature Sintering PZT Ceramics with additives of Li ₂ O ₃ -Bi ₂ O ₃ -CdO ", Proceedings of Eighth IEEE International Symposium on Applications of Ferroelectrics.) There is a problem of increasing the dielectric loss tangent and worsening the piezoelectric parameter. This liquid phase formed during sintering also has a problem of easily reacting with silver (Ag) or silver (Ag) -palladium (Pd) electrodes and making it difficult to co-sinter the multilayer piezoelectric element.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is a soft system which can be sintered at a temperature much lower than the melting point of silver (Ag), so that it can be co-sintered with the silver (Ag) electrode. It is to provide a piezoelectric ceramic composition.

Another object of the present invention is to provide a piezoelectric ceramic device using the piezoelectric ceramic composition.

Still another object of the present invention is to provide a multilayer piezoelectric ceramic device using the piezoelectric ceramic composition.

The above and other objects of the present invention can be achieved by the present invention described below.

In order to achieve the above object, the present invention provides [(Pb _1-mn Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _1-x ) _1-ab Ni _a W _b ] O ₃ (where , m, n, x, y, a and b are 0.00 ≦ m ≦ 0.18 as molar ratio, 0.00 ≦ n ≦ 0.18, 0.00 ≦ (m + n) ≦ 0.21, 0.40 ≦ x ≦ 0.60, and 0.000 <y ≤ 0.04, 0.00 ≤ a ≤ 0.02, and 0.00 <b ≤ 0.02.) A soft piezoelectric ceramic composition comprising a ceramic and 0.001 to 2 wt% or less of cadmium oxide (CdO) is provided.

The present invention also provides a piezoelectric ceramic device comprising a piezoelectric ceramic obtained by sintering the above piezoelectric ceramic composition at 980 ° C. or lower.

The present invention also provides a piezoelectric ceramic device comprising a piezoelectric ceramic layer obtained by co-sintering the piezoelectric ceramic composition with silver (Ag) internal electrode at 960 ° C. or lower.

The present invention also provides a multilayer piezoelectric ceramic device comprising a piezoelectric ceramic layer obtained by co-sintering the piezoelectric ceramic composition with a silver (Ag) -palladium (Pd) internal electrode at 1050 ° C. or lower.

Hereinafter, the present invention will be described in more detail.

The soft piezoelectric ceramic composition of the present invention is an essential component [(Pb _1-mn Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _1-x ) _1-ab Ni _a W _b ] O ₃ , where m, n, x, y, a and b are molar ratios of 0.00 ≦ m ≦ 0.18, 0.00 ≦ n ≦ 0.18, 0.00 ≦ (m + n) ≦ 0.21, 0.40 ≦ x ≦ 0.60 And 0.000 <y ≦ 0.04, 0.00 ≦ a ≦ 0.02, and 0.00 <b ≦ 0.02.) Ceramic and cadmium oxide (CdO).

[(Pb _1-mn Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _1-x ) _1-ab Ni _a W _{b which} is an essential component of the soft piezoelectric ceramic composition of the present invention ] O ₃ ceramics are used at the base matrix of Pb (Zr, Ti) O ₃ Sr ²⁺ , Ba ²⁺ and Bi ³⁺ instead of Pb ²⁺ replace Zr ⁴⁺ or Ti ⁴⁺ Ni ²⁺ and W ⁶⁺ are substituted.

Sr ²⁺ or Ba ²⁺ increases the dielectric constant without significantly changing the coupling factor and elastic modulus, so the piezoelectric with a decrease in the Curie temperature (Tc) constant, d ₃₃ ).

Bi ³⁺ substitutes for Pb ²⁺ or Substitution of Zr ⁴⁺ or Ti ⁴⁺ by W ⁶⁺ forms a vacancy at the Pb ²⁺ site of PZT and imparts the piezoelectric properties of the soft piezoelectric ceramic as follows.

1) high piezoelectric constant,

2) high electro-mechanical coupling coefficient,

3) high dielectric loss,

4) low mechanical quality factor.

Substitution of O ^2- with F ⁻ also forms vacancy at the Pb ²⁺ site. Ni ²⁺ increases the piezoelectric constant (piezoelectric parameter) and, Ni ²⁺ influences the maximum amount of W ⁶⁺ to be added according to the difference in sizes and valence states (valence state) compared to the W ^6+.

Bi ³⁺ effectively increases densification in the early stages of sintering at reduced temperatures, but does not significantly deteriorate the piezoelectric parameters and is introduced into the matrix of the piezoceramic at the end of the sintering process. Form a transient liquid phase.

[(Pb _1-mn Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _1-x ) _1-ab Ni _a W _b ] O _{3 In} ceramics m, n, x, y, a and b is a molar ratio: 0.00 ≦ m ≦ 0.18, 0.00 ≦ n ≦ 0.18, 0.00 ≦ (m + n) ≦ 0.21, 0.40 ≦ x ≦ 0.60, 0.000 <y ≦ 0.04, 0.00 ≦ a ≦ 0.02 , 0.00 <b ≦ 0.02.

Positive of Bi ³⁺ y is a molar ratio of 0.000 <y ≦ 0.04, a quantity of Ni ²⁺ , a is a molar ratio of 0.00 ≦ a ≦ 0.02, W ⁶⁺ , and b is a molar ratio of 0.00 <b ≦ 0.02 and sintered at a reduced temperature It is a soft piezoelectric ceramic material, which is preferable to obtain piezoelectric parameters such as piezoelectricity (d ₃₃ ) and electromechanical coupling coefficient (k _p ) to practical levels, and the ratio of y, a and b is 1: It is more preferable that it is 0.5-1: 0.33-0.5. If it is lower than the lower limit or higher than the upper limit, the piezoelectric parameter d ₃₃ or the electro-mechanical parameter is greatly reduced by the soft piezoelectric ceramic. M, the amount of Sr, is 0.00≤m≤0.18 as molar ratio, and n, the amount of Ba is molar ratio, which is required to have a value of 0.00≤n≤0.18, 0.00≤ (m + n) ≤0.21. It is desirable to obtain Curie point, Tc). X, the relative amount of Zr to Ti, has a molar ratio of 0.4 to 0.6 and has a piezoelectric modulus (d ₃₃ ), an electromechanical coupling coefficient (k _p ), a temperature coefficient, and a dielectric constant. It is desirable to optimize the required piezoelectric parameters, such as constant or resonant frequency.

The soft piezoelectric ceramic composition of the present invention includes cadmium oxide (CdO) as an sintering aid as an essential component, and at least one sintered selected from the group consisting of lead (II) oxide (PbO) and lithium fluoride (LiF). It is preferable to further include an adjuvant.

These sintering aids form a transient liquid phase at low temperatures with Bi ₂ O ₃ and assist in densification during sintering. All elements of the sintering aid or Bi ₂ O ₃ have some degree of solubility in the PZT matrix, and most of the elements in the intermediate liquid phase are introduced into the PZT matrix later in the sintering process. does not deteriorate the piezoelectric parameters.

The sintering aid effectively increases densification in the early stages of sintering at reduced temperatures, but does not significantly deteriorate the piezoelectric parameters and is introduced into the matrix of the piezoceramic at the end of the sintering process. to form a liquid phase.

The content of cadmium oxide (CdO) in the sintering aid is preferably 0.001 to 2% by weight or less. Meanwhile, the content of lead oxide (II) (PbO) in the sintering aid is preferably 0.001 to 2% by weight or less, and the content of lithium fluoride (LiF) is preferably 0.001 to 1.6% by weight or less. Beyond these conditions, the soft piezoelectric ceramic material sintered at the reduced temperature does not obtain the piezoelectric parameters such as d ₃₃ , k _p, etc. to the practical level, and the piezoelectric parameters d ₃₃ ). Alternatively, the electro-mechanical parameter is very much reduced by soft piezoelectric ceramics.

Hereinafter, the present invention will be described in detail with Examples and Experimental Examples.

However, the following examples are only one preferred embodiment of the present invention and the present invention is not limited to the following examples.

EXAMPLE

[Production of Soft Piezoceramic Composition]

Lead oxide (PbO), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), strontium carbonate (SrCO ₃ ), barium carbonate (BaCO ₃ ), cadmium oxide (CdO), bismuth oxide (Bi ₂ O ₃ ), and Lithium fluoride (LiF) is used as starting material. Examples 1 to 38 are weighed into compositions according to Table 1.

m n x y a b CdO weight% PbO weight% LiF weight% Example 1 0.06 0 0.535 0.02 0.01 0.0067 0.80 0.20 0.16 Example 2 0.035 0.025 0.535 0.02 0.01 0.0067 0.80 0.20 0.16 Example 3 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.20 0.16 Example 4 0.06 0 0.535 0.02 0.01 0.0067 1.6 0.20 0.16 Example 5 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.00 0.16 Example 6 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.50 0.16 Example 7 0.06 0 0.535 0.02 0.01 0.0067 1.2 1.00 0.16 Example 8 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.20 0.00 Example 9 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.20 0.50 Example 10 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.20 1.00 Example 11 0.06 0 0.535 0.02 0.01 0.0067 1.2 0.20 1.50 Example 12 0.06 0 0.535 0.03 0.015 0.0100 1.2 0.20 0.16 Example 13 0.06 0 0.535 0.04 0.02 0.0130 1.2 0.20 0.16 Example 14 0.035 0.025 0.535 0.02 0.01 0.0067 1.2 0.20 0.16 Example 15 0 0.06 0.535 0.02 0.01 0.0067 1.2 0.20 0.16 Example 16 0.10 0 0.535 0.02 0.01 0.0067 1.2 0.20 0.16 Example 17 0.06 0 0.515 0.02 0.01 0.0067 1.2 0.20 0.16 Example 18 0.06 0 0.525 0.02 0.01 0.0067 1.2 0.20 0.16 Example 19 0.06 0 0.545 0.02 0.01 0.0067 1.2 0.20 0.16 Example 20 0.06 0 0.555 0.02 0.01 0.0067 1.2 0.20 0.16 Example 21 0.06 0 0.53 0.02 0.01 0.0067 1.2 0.20 1.00 Example 22 0.06 0 0.525 0.02 0.01 0.0067 1.2 0.20 1.00 Example 23 0.06 0 0.525 0.02 0.01 0.0067 1.2 0.20 1.50 Example 24 0.06 0 0.520 0.02 0.01 0.0067 1.2 0.20 1.00 Example 25 0.06 0 0.510 0.02 0.01 0.0067 1.2 0.20 1.00 Example 26 0.06 0 0.500 0.02 0.01 0.0067 1.2 0.20 1.00 Example 27 0.06 0 0.535 0.025 0.0125 0.0125 1.2 0.20 0.16 Example 28 0.06 0 0.535 0.025 0.0167 0.0083 1.2 0.20 0.16 Example 29 0.06 0 0.525 0.025 0.0125 0.0125 1.2 0.20 0.16 Example 30 0.06 0 0.525 0.025 0.0167 0.0083 1.2 0.20 0.16 Example 31 0.08 0.07 0.525 0.025 0.0125 0.0083 1.2 0.20 0.16 Example 32 0.08 0.07 0.535 0.025 0.0125 0.0083 1.2 0.20 0.16 Realization33 0.06 0 0.535 0.020 0.0100 0.0150 1.2 0.20 0.15 Example 34 0.06 0 0.535 0.020 0.0067 0.0150 1.2 0.20 0.16 Example 35 0.06 0 0.535 0.020 0.0067 0.0125 1.2 0.20 0.16 Example 36 0.06 0 0.535 0.020 0.0000 0.0150 1.2 0.20 0.16 Example 37 0.06 0 0.535 0.000 0.0100 0.0150 1.2 0.20 0.16 Example 38 0.06 0 0.535 0.040 0.0100 0.0067 1.2 0.20 0.16 Comparative Example 1 0.06 0 0.535 0.025 0.0250 0.0083 1.2 0.20 0.16 Comparative Example 2 0.06 0 0.525 0.025 0.025 0.0083 1.2 0.20 0.16 Comparative Example 3 0.06 0 0.535 0.020 0.0100 0.0000 1.2 0.20 0.16

[Comparative Examples 1 to 3]

Comparative Examples 1, 2, and 3 were prepared by the composition according to Table 1 above.

The weighed material is wet mixed in an atrium mill using deionized water and the dried cake is calcined at 750-875 ° C. for 2 hours. The calcined material is ground in an atrium mill to reduce the particle size to an average size of about 0.8 microns. The ground powder is dried and then granulated with 10% PVA solution. PVA amount is 2% by weight of the ground powder. A green disk 25 mm in diameter and 2.5 mm thick with granulated powder is made at 1,000 Kg / cm ² pressure. The compressed green disk is sintered at 920-1000 ° C. for 2 hours. Ag paste is printed on both surfaces and burned at 700 to 820 ° C for 15 minutes. The electrodeled disc is polarized by applying a 3-4 kV / mm voltage in a silicon oil bath at 120-140 ° C. for 15 minutes. Dielectric constant and dielectric loss tangent were measured using an LCR meter at 1 kHz. Piezoelectric modulus (d ₃₃ ) was measured using a Berlincourt d ₃₃ meter. Planar coupling coefficients and mechanical quality factors are measured using the Impedance / Gain-Phase analyzer, the resonant frequency, anti-resonant frequency, and resonance impedance. Calculated with capacitance measured with and LCR meter. Density was calculated with the measured diameter and thickness.

[Characteristics of Soft Piezoelectric Ceramic Compositions]

The measured piezoelectric properties of the examples and comparative examples are shown in Tables 2, 3, 4 and 5.

Table 2 is a table showing piezoelectric properties when the compositions of Examples and Comparative Examples were sintered at 985 ° C.

ρ (g / cm ³ ) ε ₃₃ ^T / ε ₀ tanδ Electromechanical coefficients (Kp) Mechanical Quality Factor (Qm) Piezoelectricity (d ₃₃ ) Example 1 7.62 2410 0.018 0.66 59 526 Example 2 7.43 1905 0.018 0.61 62 455 Example 3 7.58 2540 0.017 0.65 58 523 Example 4 7.53 2250 0.020 0.66 57 574 Example 5 7.56 2360 0.018 0.66 54 552 Example 6 7.53 2190 0.018 0.67 56 548 Example 7 7.56 2020 0.018 0.65 61 510 Example 8 7.55 2330 0.019 0.66 55 544 Example 9 7.45 1550 0.013 0.60 84 396 Example 10 7.38 1440 0.015 0.59 88 386 Example 11 7.37 1540 0.020 0.55 81 398 Example 12 7.50 1960 0.020 0.65 56 509 Example 13 7.58 2330 0.010 0.61 45 492 Example 14 7.59 1680 0.018 0.65 66 461 Example 15 7.61 1060 0.021 0.61 78 317 Example 16 7.47 2820 0.004 0.58 60 481 Example 17 7.57 2140 0.014 0.60 74 452 Example 18 7.60 2460 0.016 0.64 66 533 Example 19 7.57 1350 0.020 0.63 72 422 Example 20 7.54 1060 0.022 0.60 78 340 Example 21 7.43 1800 0.019 0.58 74 421 Example 22 7.45 1954 0.016 0.60 77 450 Example 23 7.35 1755 0.015 0.58 64 428 Example 24 7.45 1985 0.013 0.61 75 473 Example 25 7.50 1777 0.013 0.58 82 400 Example 26 7.43 1620 0.010 0.54 95 346 Example 27 7.47 2230 0.021 0.65 68 540 Example 28 7.41 1705 0.021 0.42 76 283 Example 29 7.57 2570 0.014 0.61 70 475 Example 30 7.40 1640 0.020 0.37 86 221 Example 31 7.35 3210 0.007 0.51 52 467 Example 32 7.42 3400 0.014 0.50 43 455 Example 33 7.61 2460 0.004 0.63 58 553 Example 34 7.62 2380 0.004 0.60 60 513 Example 35 7.62 2380 0.004 0.63 61 510 Example 36 7.62 2210 0.006 0.55 63 435 Example 37 7.56 2255 0.003 0.65 71 535 Example 38 7.60 2305 0.008 0.60 51 508 Comparative Example 1 7.36 1655 0.028 0.40 76 276 Comparative Example 2 7.36 1500 0.024 0.32 85 206 Comparative Example 3 7.44 1440 0.011 0.33 83 210

As can be seen in Table 2, Examples 1 to 38 have a piezoelectric coefficient (d ₃₃ ) of 317 to 574, an electromechanical coefficient of 0.42 to 0.67, and ε ₃₃ ^T / ε of 1060 to 3210 when sintered at 985 ° C. ₀ was shown. It can be seen that Examples 1 to 38 show higher piezoelectricity (d ₃₃ ), higher electromechanical coupling coefficient (Kp), and higher ε ₃₃ ^T / ε ₀ than Comparative Examples 1 to 3.

Table 3 is a table showing piezoelectric properties when the compositions of Examples and Comparative Examples were sintered at 960 ° C.

ρ (g / cm ³ ) ε ₃₃ ^T / ε ₀ tanδ Electromechanical coefficients (Kp) Mechanical Quality Factor (Qm) Piezoelectricity (d ₃₃ ) Example 1 6.34 1300 0.058 0.50 76 419 Example 2 7.15 1460 0.012 0.40 78 256 Example 3 7.48 2245 0.009 0.60 50 478 Example 4 7.53 2310 0.020 0.65 61 525 Example 5 7.51 2260 0.020 0.64 61 509 Example 6 7.48 2100 0.020 0.65 60 500 Example 7 7.54 2100 0.023 0.56 64 375 Example 8 7.48 2340 0.020 0.63 61 510 Example 9 7.51 1580 0.015 0.62 84 407 Example 10 7.42 1610 0.020 0.57 81 394 Example 11 7.35 1660 0.023 0.51 78 345 Example 12 7.58 2200 0.021 0.64 57 526 Example 13 7.50 2120 0.029 0.61 54 469 Example 14 7.50 1660 0.023 0.63 64 414 Example 15 7.54 1120 0.024 0.59 74 326 Example 16 7.44 2875 0.004 0.60 58 500 Example 17 7.55 2185 0.014 0.59 73 428 Example 18 7.56 2440 0.015 0.64 65 518 Example 19 7.57 1400 0.020 0.64 70 405 Example 20 7.58 1050 0.021 0.58 79 333 Example 21 7.34 1680 0.019 0.58 83 400 Example 22 7.42 1770 0.014 0.61 81 432 Example 23 7.31 1710 0.015 0.58 86 412 Example 24 7.45 1880 0.014 0.61 81 455 Example 25 7.45 1810 0.013 0.58 71 379 Example 26 7.46 1630 0.011 0.55 92 354 Example 27 7.41 2000 0.004 0.58 65 483 Example 28 7.44 1640 0.010 0.53 70 425 Example 29 7.48 2470 0.002 0.63 64 502 Example 30 7.45 1980 0.004 0.57 66 466 Example 31 7.35 3470 0.011 0.57 50 546 Example 32 7.41 3650 0.016 0.55 42 511 Example 33 7.54 2410 0.007 0.62 58 505 Example 34 7.61 2275 0.008 0.55 60 469 Example 35 7.62 2250 0.008 0.61 63 493 Example 36 7.51 2050 0.024 0.52 63 367 Example 37 7.32 1940 0.021 0.61 69 473 Example 38 7.45 2055 0.023 0.62 52 482 Comparative Example 1 6.96 1260 0.052 0.37 75 255 Comparative Example 2 7.22 1545 0.015 0.41 75 281 Comparative Example 3 7.11 1305 0.031 0.33 79 204

As can be seen in Table 3, Examples 1 to 38 have a piezoelectric coefficient (d ₃₃ ) of 326 to 526, an electromechanical coefficient of 0.52 to 0.65, and an ε ₃₃ ^T / ε of 1580 to 2470 when sintered at 960 ° C. ₀ was shown. It can be seen that Examples 1 to 36 show higher piezoelectricity (d ₃₃ ), higher electromechanical coupling coefficient (Kp), and higher ε ₃₃ ^T / ε ₀ than Comparative Examples 1 to 3.

Table 4 is a table showing piezoelectric properties when the compositions of Examples and Comparative Examples were sintered at 950 ° C.

ρ (g / cm ³ ) ε ₃₃ ^T / ε ₀ tanδ Electromechanical coefficients (Kp) Mechanical Quality Factor (Qm) Piezoelectricity (d ₃₃ ) Example 1 6.53 1410 0.055 0.53 68 426 Example 2 7.27 1760 0.004 0.58 67 430 Example 3 7.56 2150 0.006 0.65 60 470 Example 4 7.46 2200 0.008 0.66 66 494 Example 5 7.52 2200 0.008 0.63 62 493 Example 6 7.57 2190 0.008 0.66 64 510 Example 7 7.43 2000 0.008 0.64 65 452 Example 8 7.52 2200 0.007 0.65 63 485 Example 9 7.52 1620 0.002 0.63 70 394 Example 10 7.48 1400 0.003 0.60 90 386 Example 11 7.34 1600 0.008 0.52 80 361 Example 12 7.56 2270 0.009 0.65 58 500 Example 13 7.55 2400 0.013 0.58 55 450 Example 14 7.53 1750 0.011 0.64 64 440 Example 15 7.60 1155 0.022 0.59 75 330 Example 16 7.42 2800 0.004 0.60 59 507 Example 17 7.58 2220 0.002 0.59 70 435 Example 18 7.54 2400 0.004 0.62 64 470 Example 19 7.59 1500 0.008 0.59 68 430 Example 20 7.56 1190 0.009 0.61 72 368 Example 21 7.40 2010 0.028 0.43 62 310 Example 22 7.42 2020 0.027 0.44 65 340 Example 23 7.34 1910 0.029 0.37 70 266 Example 24 7.44 2050 0.025 0.41 68 290 Example 25 7.37 1860 0.016 0.50 80 340 Example 26 7.45 1740 0.018 0.36 83 240 Example 27 7.51 2090 0.019 0.63 59 477 Example 28 7.14 1425 0.026 0.41 82 266 Example 29 7.57 2410 0.017 0.62 65 473 Example 30 7.53 1540 0.024 0.32 83 185 Example 31 7.34 3240 0.010 0.52 50 471 Example 32 7.43 3630 0.013 0.57 41 559 Example 33 7.53 1930 0.004 0.56 69 439 Example 34 7.50 2100 0.005 0.64 47 483 Example 35 7.59 1990 0.009 0.58 65 411 Example 36 7.54 1990 0.020 0.51 72 381 Example 37 7.54 1985 0.019 0.61 71 481 Example 38 7.60 2190 0.023 0.57 57 457 Comparative Example 1 7.36 1640 0.022 0.40 77 276 Comparative Example 2 7.67 1424 0.038 0.34 94 213 Comparative Example 3 7.17 1250 0.038 0.31 88 189

As can be seen in Table 4, Examples 1 to 38 have piezoelectric coefficients (d ₃₃ ) of 266 to 559, electromechanical coupling coefficients of 0.32 to 0.66, and ε ₃₃ ^T / ε of 1155 to 3630 when sintered at 950 ° C. ₀ was shown. It can be seen that Examples 1 to 38 show higher piezoelectricity (d ₃₃ ), higher electromechanical coupling coefficient (Kp), and higher ε ₃₃ ^T / ε ₀ than Comparative Examples 1 to 3.

Table 5 is a table showing piezoelectric properties when the compositions of Examples and Comparative Examples were sintered at 938 ° C.

ρ (g / cm ³ ) ε ₃₃ ^T / ε ₀ tanδ Electromechanical coefficients (Kp) Mechanical Quality Factor (Qm) Piezoelectricity (d ₃₃ ) Example 1 7.57 2170 0.021 0.65 60 457 Example 2 7.20 1600 0.018 0.56 68 441 Example 3 7.54 2100 0.019 0.63 60 518 Example 4 7.64 2100 0.008 0.64 64 490 Example 5 7.54 2050 0.008 0.62 62 455 Example 6 7.66 2000 0.007 0.64 69 490 Example 7 7.60 1705 0.009 0.61 66 385 Example 8 7.54 2100 0.007 0.63 63 460 Example 9 7.41 1160 0.002 0.62 77 438 Example 10 7.42 1460 0.034 0.59 89 390 Example 11 7.35 1560 0.008 0.51 90 340 Example 12 7.55 1900 0.009 0.65 64 490 Example 13 7.56 1970 0.009 0.62 55 460 Example 14 7.51 1700 0.010 0.61 66 430 Example 15 7.49 1240 0.020 0.61 76 306 Example 16 7.48 2700 0.003 0.59 59 485 Example 17 7.56 2200 0.002 0.59 72 446 Example 18 7.62 2300 0.004 0.62 66 474 Example 19 7.58 1490 0.010 0.63 69 415 Example 20 7.54 1155 0.021 0.60 78 354 Example 21 7.43 1670 0.005 0.57 83 390 Example 22 7.41 1760 0.004 0.60 76 423 Example 23 7.36 1740 0.019 0.56 80 395 Example 24 7.48 1890 0.018 0.59 76 453 Example 25 7.43 1830 0.015 0.58 80 410 Example 26 7.47 1700 0.013 0.53 90 355 Example 27 7.24 2080 0.020 0.58 65 440 Example 28 6.90 1270 0.059 0.38 89 251 Example 29 7.48 2320 0.016 0.61 66 479 Example 30 7.50 1490 0.020 0.26 98 156 Example 31 7.39 3190 0.026 0.56 49 495 Example 32 7.37 3420 0.030 0.57 42 560 Example 33 7.57 2235 0.021 0.61 63 498 Example 34 7.62 2020 0.020 0.60 64 456 Example 35 7.57 1990 0.019 0.60 64 463 Example 36 7.52 1985 0.022 0.51 67 378 Example 37 7.47 1890 0.021 0.62 72 471 Example 38 7.51 1990 0.022 0.61 56 482 Comparative Example 1 6.68 1232 0.107 0.38 90 264 Comparative Example 2 6.70 1400 0.249 0.32 75 227 Comparative Example 3 7.06 1306 0.011 0.32 78 199

As can be seen in Table 5, Examples 1 to 38 have piezoelectric coefficients (d ₃₃ ) of 156 to 560, electromechanical coupling coefficients of 0.26 to 0.65, and ε ₃₃ ^T / ε of 1155 to 3420 when sintered at 938 ° C. ₀ was shown. It can be seen that Examples 1 to 38 show higher piezoelectricity (d ₃₃ ), higher electromechanical coupling coefficient (Kp), and higher ε ₃₃ ^T / ε ₀ than Comparative Examples 1 to 3.

As can be seen in Tables 2, 3, 4 and 5, Examples 1 to 38, when sintered at 990 ℃ or less, high piezoelectric coefficient (d ₃₃ ), high electric field coupling coefficient (Kp), high dielectric constant It has been found to show good characteristics of typical soft piezoelectric ceramic materials such as (dielectric constant) and the like. Examples 1 to 38 showed good piezoelectric parameters even when sintered below 960 ° C., thus making it possible to co-sinter with pure silver (Ag) internal electrodes.

EXAMPLE

[Production of Multi-layer Piezoelectric Plates with Pure Silver Internal Electrodes]

A multilayer piezoelectric plate with a sterling silver internal electrode was prepared with the soft piezoelectric ceramic composition of the present invention. Example 3 above was chosen as an example.

The manufacture of multilayer piezoelectric plates consists of the synthesis of piezoelectric ceramic materials, the manufacture of green sheets, electrode pattern printing, multilayer lamination, co-sintering of laminated green bars, external electrode treatment with silver (Ag) paste, and polarization. The calcined material is a binder solution consisting of polyvinyl butyral (PVB), dibutyl phthalate (DBP; dibutyl phthalate), fish oil, methyl ethyl ketone (MEK) and toluene (toluene). And mix in a ball mill for 36 hours. The ground slurry is deaired under vacuum and a 120 micron thick tape is formed on the PET film using a doctor blade casting machine. The green tape is cut into sheets of 150 mm x 150 mm with alignment holes. The alternating internal electrodes are printed on a green sheet using sterling silver paste and dried in a continuous oven. The printed green sheet is laminated using the alignment holes in the laces and heat-pressed under 85 ° C vacuum. The hot-laminated green bar is cut into each green element. The binder as well as the organics in the green element were removed at 260 ° C. and sintered at 940 ° C. for 2 hours. The external electrode was screen printed using silver (Ag) paste and baked at 780 ° C. Polarization consisted of a poling voltage of 450 VDC in a 130 ° C. silicon oil bath. The size of the multilayer piezoelectric plate is 5.13 mm x 5.13 mm x 1.04 mm and consists of 19 piezoelectric active layers with 20 internal electrodes. Each layer was 50 microns thick and cover sheets were formed on the bottom and surface of the plate. 1 and 2 are cross-sectional views of a multilayer piezoelectric plate co-sintered with silver (Ag) internal electrodes. The surface of the silver internal electrode was excellent without noticeable holes or delamination, showing very small resonance impedance and excellent piezoelectric properties. Although the silver (Ag) paste co-sintered at 950 ° C., there was no noticeable reaction with the PZT matrix made from the soft piezoelectric ceramic composition of Example 3. 3 is a graph showing the impedance / phase characteristics of the manufactured plate. The resonance frequency is 381.5 kHz depending on the width of the plate and the resonance frequency is 80 mohm. The maximum phase angle is 87.26 degrees.

This multilayer piezoelectric plate is just an example and manufactures many other multilayer piezoceramic devices with pure silver (Ag) internal electrodes such as, for example, multilayer stacked actuators, multilayer sensors, multilayer bimorphs, and the like. can do.

As described above, the soft piezoelectric ceramic composition of the present invention has a high piezoelectric constant and an electro-mechanical coupling coefficient, and can be co-sintered with the silver electrode.

According to the soft piezoelectric ceramic composition of the present invention, a piezoelectric ceramic device such as a multilayer piezoelectric actuator or the like having a pure silver internal electrode which can reduce the cost of the electrode compared to the silver (Ag) -palladium (Pd) internal electrode. Can be prepared.

1 is a cross-sectional view of a multilayer piezoelectric plate co-sintered with silver (Ag) internal electrodes, which is one embodiment of a piezoelectric ceramic device according to the present invention.

2 is a cross-sectional view of a multilayer piezoelectric plate co-sintered with silver (Ag) internal electrodes, which is one embodiment of a piezoelectric ceramic device according to the present invention.

Figure 3 is a graph showing the impedance / phase characteristics of a multilayer piezoelectric plate as one embodiment of a piezoelectric ceramic device according to the present invention.

Claims (9)

Ceramic represented by the following formula; And, 0.001 to 2 wt% or less of cadmium oxide (CdO); Soft (pie) -based piezoelectric ceramic composition comprising a. <Formula> [(Pb _1-mn Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _1-x ) _1-ab Ni _a W _b ] O ₃ Wherein m, n, x, y, a and b are molar ratios of 0.00 ≦ m ≦ 0.18, 0.00 ≦ n ≦ 0.18, 0.00 ≦ (m + n) ≦ 0.21, 0.40 ≦ x ≦ 0.60, and 0.000 <y <0.04, 0.00 <a <0.02, and 0.00 <b <0.02. The method of claim 1, wherein the soft (pie) piezoelectric ceramic composition. A soft piezoelectric ceramic composition further comprising at least one sintering aid selected from the group consisting of lead (II) oxide (PbO) and lithium fluoride (LiF). The method of claim 2, wherein the lead (II) oxide (PbO) is, Soft piezoelectric ceramic composition, characterized in that 0.001 to 2% by weight or less. The method of claim 2, wherein the lithium fluoride (LiF), Soft piezoelectric ceramic composition, characterized in that 0.001 to 1.6% by weight or less. The method of claim 1 or 2, The ratio of y, a, and b is 1: 0.5 to 1: 0.33 to 0.5 of the soft (soft) piezoelectric ceramic composition, characterized in that. A piezoelectric ceramic device comprising a piezoelectric ceramic obtained by sintering the piezoelectric ceramic composition of claim 1 or 2 at 980 캜 or lower. A multilayer piezoelectric ceramic device comprising a piezoelectric ceramic layer obtained by co-sintering the piezoelectric ceramic composition of claim 1 or 2 together with silver (Ag) internal electrodes at 960 ° C. or less. A multilayer piezoelectric ceramic device comprising a piezoelectric ceramic layer obtained by co-sintering the piezoelectric ceramic composition of claim 1 or 2 together with a silver (Ag) -palladium (Pd) internal electrode. The multilayer piezoelectric ceramic device of claim 8, wherein the amount of palladium (Pd) is 20 parts by weight based on 100 parts by weight of the silver (Ag) and the palladium (Pd).