JPH0558645A - Piezoelectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a material, sinterable at a low temperature, having a high resistivity and a large piezoelectric strain constant and useful as actuators, especially stacked type piezoelectric elements. CONSTITUTION:The objective piezoelectric porcelain composition is expressed by the general formula (1-w)[xPb(Ni1/3Nb2/3)O3-yPbTiO3-zPbZrO3]-wPb(Me1/2 W1/2)O3 [(X+Y+Z) is 1] and the blending ratio (x), (y) and (z) are located on lines connecting the following composition points A; [(x) is 0.74; (y) is 0.25; (z) is 0.001] to B; [(x) is 0.40; (y) is 0.59; (z) is 0.01], C; [(x) is 0.40; (y) is 0.25; (z) is 0.35] and D; [(x) is 0.06; (y) is 0.59; (z) is 0.35] and within the range surrounded by the lines. Furthermore, (w) is within the range of 0.001<=(w)<=0.2 and Me is any one of Ni, Mg, Cu, Zn and Co. At least one of Mn, Cr and Fe is respectively contained in an amount of 0.005-1.0wt.% expressed in terms of MnO2, Cr2O3 and Fe2O3. Part of Pb which is the principal component is further replaced with 0.001-0.2 at least one of Ca, Ba and Sr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric ceramic composition containing lead zirconate titanate as a main component, which has particularly large piezoelectric characteristics and a low sintering temperature of about 1100 ° C. The present invention relates to a piezoelectric ceramic composition having excellent insulation performance.

[0002]

2. Description of the Related Art Conventional piezoelectric ceramic compositions containing lead zirconate titanate as a main component have a large piezoelectric constant, and are widely used as materials for actuators including piezoelectric vibrators. .. However, with this type of material, it is difficult to obtain a dense sintered body due to evaporation of lead oxide during firing, and the morphotopic phase boundary (MP
In the vicinity of B), since the piezoelectricity depends on the composition of titanium and zirconium, it is difficult to guarantee the reproducibility and uniformity of the characteristics. To remedy these drawbacks,
For example, a means for substituting a part of Pb with an appropriate amount of Ca, Sr, Mg, Ba or the like, or La, Nd, Nb, Ta, S
There is a means of adding oxides such as b, Bi, Th, and W.
The former has the advantage that the permittivity can be increased without deteriorating the piezoelectric characteristics, and the latter has the advantage that polarization is facilitated, the piezoelectric constant is increased, and the change over time is reduced.

On the other hand, in parallel with the improvement of the lead zirconate titanate, many compound perovskite type compounds having a plurality of ions having different valences at the A or B positions have been discovered as ABO ₃ type ferroelectrics. Since then, research and development on the composition of the three components with this complex perovskite type compound have been vigorously pursued. The ternary piezoelectric ceramic composition is, for example, Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbT.
There is a composition of iO ₃ -PbZrO ₃ . The characteristic of such a three-component piezoelectric ceramic composition is that the vaporization of lead oxide is less, calcination is easier, and the morphotopic is lower than that of the above-mentioned component system such as Pb (Zr, Ti) O _3. The phase boundary (MPB) extends from a point to a line, resulting in a material with properties that make it more versatile.

The Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbTi
The piezoelectric ceramic composition of the O ₃ -PbZrO ₃ system has a piezoelectric strain constant (d
Since the (constant) is extremely large, it is suitable for a piezoelectric ceramic for an actuator element.

[0005]

However, the above-mentioned P
The sintering temperature of the b (Ni _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -PbZrO ₃ -based piezoelectric ceramic composition is as high as 1200 to 1300 ° C. For this reason, when a laminated piezoelectric element is produced from this piezoelectric ceramic composition, platinum or palladium that can withstand this sintering temperature must be used as the internal electrode, which causes a problem of high manufacturing cost. If the sintering temperature can be lowered, inexpensive silver-palladium alloys can be used. When using a silver-palladium alloy as the internal electrode, if the cost of palladium is high and the content of palladium is high, the palladium undergoes an oxidation-reduction reaction during sintering, causing cracks and peeling in the laminated piezoelectric element. Therefore, the proportion of palladium is required to be 30% or less.

In order to reduce the ratio of palladium to 30% or less, it is necessary to set the sintering temperature to 1150 ° C. or less, preferably 1120 ° C. or less from the Ag-Pd system phase diagram. Therefore, Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbTiO ₃
A complicated operation such as finely pulverizing the calcined powder or performing HIP treatment is required to prepare a laminated piezoelectric element using silver-palladium for the internal electrode with the -PbZrO ₃ -based piezoelectric ceramic composition. Furthermore, the Pb (Ni _1/3 Nb
_{The 2/3} ) O ₃ -PbTiO ₃ -PbZrO ₃ -based piezoelectric ceramic composition has a relatively small specific resistance. Therefore, for example, in a multilayer piezoelectric element having a thickness of about 100 μm, the Pb ( Ni _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -PbZr
When the O ₃ -based piezoelectric ceramic composition is used, there is a problem that the reliability is low such that the voltage that can be applied is small and sufficient performance cannot be obtained, or dielectric breakdown occurs during use.

The present invention solves the above problems existing in the prior art, has a large piezoelectric characteristic, and has a sintering temperature of 11
It is an object of the present invention to provide a piezoelectric ceramic composition which has a low temperature of about 00 ° C. and has a large specific resistance and which is suitable as a material for actuators, particularly as a material for laminated piezoelectric elements.

[0008]

In order to solve the above problems, in the present invention, the general formula (1-w) {xPb (Ni _1/3 N
_{b 2/3) O 3 -yPbTiO 3 -zPbZrO} 3} -wPb (M
e _1/2 W _1/2 ) O ₃ (x + y + z = 1), and the compounding ratios x, y, z are
In this three-component composition diagram, the following composition point A: (X = 0.7
4, y = 0.25, z = .001) B: (x = 0.40, y = 0.59, z = 0.0
1) C: (x = 0.40, y = 0.25, z = 0.35) D: (x = 0.06, y
= 0.59, z = 0.35) on the line connecting them and in the composition range surrounded by this line, and w is in the range of 0.001 ≦ w ≦ 0.2,
Me is any one of Ni, Mg, Cu, Zn and Co, and at least one of Mn, Cr and Fe is converted into MnO ₂ , Cr ₂ O ₃ and Fe ₂ O ₃ , respectively, and 0.00
5-1. A technical means was adopted in which the content of Pb in the main component was 0 wt% and a part of Pb in the main component was replaced with at least one of Ca, Ba and Sr of 0.001 to 0.2.

[0009]

[Function] Pb (Ni _1/3 Nb _2/3 ) O ₃ -Pb which is the main component
The reason why TiO ₃ —PbZrO ₃ is limited to the above range is that the electromechanical coupling coefficient Kp or the relative permittivity ε T _{33 is} remarkably lowered in the composition other than the above range. The amount of strain generated when a laminated piezoelectric element is used is proportional to the piezoelectric strain constant, which is one of the material properties of piezoelectric ceramic compositions. This piezoelectric strain constant (d31) is calculated by equation 1.

[Number 1] d31 = _{[(1-σ) S 11 E} · εT 33 · ε 0/2 ] ^1/2 · Kp ^(σ: Poisson's ratio, S ₁₁ E: elastic compliance,
ε ₀ : Dielectric constant of vacuum) σ in the number 1 and S ₁₁ E is at most σ = 0.25 to 0.35 and S ₁₁ E = 11 to 16 × 10 in the PZT-based piezoelectric material.
^Since it is in the range of ^-12 m ² / N, d 31 is almost proportional to the product of Kp and the square root of ε T ₃₃ . For this reason, the piezoelectric strain constant (d constant) is significantly reduced outside the above-mentioned limited range.

Pb (Me _1/2 W _1/2 ) O ₃ (Me is Ni,
Any one of Mg, Cu, Zn, Co) 0.001
When ≦ w ≦ 0.2 is contained, the sintering temperature can be significantly lowered without lowering Kp and εT ₃₃ . When w <0.001, the sintering temperature cannot be set to 1120 ° C or lower. When w> 0.2, the decrease in Kp is remarkable. At least one of Mn, Cr, and Fe is Mn.
In terms of _{O 2, Cr 2 O 3,} Fe 2 O 3, 0.005~
When 1.0 wt% is added, the specific resistance can be significantly improved without lowering Kp and ε T ₃₃ . If the added amount is less than 0.005% by weight, the specific resistance does not increase, and if the added amount exceeds 1.0% by weight, the Kp is significantly reduced. Substitution of Pb in the main component with at least one of Ca, Ba and Sr increases ε T ₃₃ . If the amount of substitution is less than 0.001, the effect of substitution is insufficient, and if it exceeds 0.2, the Kp is significantly lowered and the sintering temperature exceeds 1120 ° C.

[0011]

EXAMPLES The effects of the present invention will be specifically described below with reference to examples. Lead oxide (PbO), titanium oxide (Ti
O ₂ ), zirconium oxide (ZrO ₂ ), nickel oxide (NiO), niobium oxide (Nb ₂ O ₅ ), manganese oxide (MnO ₂ ), iron oxide (Fe ₂ O ₃ ), chromium oxide (Cr ₂
O ₃ ), tungsten oxide (WO ₃ ), magnesium oxide (MgO), copper oxide (CuO), zinc oxide (Zn)
O), cobalt oxide (CoO), and strontium carbonate (SrCO ₃ ) raw materials were weighed so as to have the compositions shown in Tables 1 and 2, and mixed in a ball mill for 2 hours.
The obtained mixture was tentatively molded, then calcinated in air at 850 ° C. for 2 hours, and further pulverized by a ball mill for 2 hours. After granulating this, a molded product having a diameter of 20 mm and a length of 15 mm was prepared by press molding. This compact was sintered in oxygen for 2 hours in a state of being hermetically sealed in a container made of alumina or magnesia. The obtained sintered body was cut and polished to form a device having a diameter of 16 mm and a thickness of 0.8 mm, and electrodes made of Cr-Au were formed on both end faces thereof. A direct current voltage of 3 kV / mm was applied in silicon oil at a voltage of 15 kV / mm. A polarization treatment was performed by applying for a minute.

[0012]

[Table 1]

[0013]

[Table 2]

Tables 3 and 4 show the characteristics obtained with each composition. Composition Nos. 1, 2, 3, and 4 are A in FIG. 1, respectively.
The composition of B, C, and D corresponds to the composition when w = 0. The main component, Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -Pb
ZrO ₃ is K within the composition range surrounded by A, B, C and D.
A large displacement amount can be obtained when the laminated piezoelectric element has a large p, εT ₃₃ . Composition No. 5 has the same composition as No. 1 with Pb (Ni
_Although the composition has _1/2 W _1/2 ) O ₃ added, it is clear that the sintering temperature is lowered. From the results of composition Nos. 6 to 11, it can be seen that the specific resistance is significantly improved by adding MnO ₂ . From the results of No. 11, it can be seen that when the added amount of MnO ₂ exceeds 1% by weight, the Kp is remarkably lowered and it becomes unsuitable as a material for actuators. No.12 to 1
From the results of No. 7, the sintering temperature decreases as the amount of Pb (Ni _1/2 W _1/2 ) O ₃ added increases, but when w exceeds 0.2, Kp remarkably decreases, so w is 0. .2 or less. Composition Nos. 18 to 33 are Pb (Me _1/2 W _1/2 ) O ₃
The characteristics when Me of Mg is Mg, Cu, Zn and Co are shown. In any case, the same effect as that when Me is Ni is shown. From the results of composition Nos. 34 to 38, Pb
By substituting a part of Sr with Sr, ε T ₃₃ is further increased, but if the substitution amount exceeds 0.2, Kp is remarkably lowered, and it is not preferable as a material for an actuator.

In Tables 5 and 6, instead of MnO ₂ , C
When r ₂ O ₃ was added, Tables 7 and 8 show the compositions and the obtained properties respectively when Fe ₂ O ₃ was added instead of MnO ₂ . In any case, MnO ₂
It can be seen that the same effect as in the case of adding is obtained.

[0016]

[Table 3]

[0017]

[Table 4]

[0018]

[Table 5]

[0019]

[Table 6]

[0020]

[Table 7]

[0021]

[Table 8]

As is clear from the above results, the piezoelectric ceramic composition of the present invention has an optimum sintering temperature of 1120 ° C. or lower, a large specific resistance, and a large Kp, εT ₃₃ . When Ca and Ba were used instead of Sr, almost the same results as in Table 1 were obtained.

[0023]

As described above, since the present invention has a sintering temperature of 1120 ° C. or lower, it is possible to use inexpensive silver / palladium electrodes when used as a laminated piezoelectric element, and Since it has a large piezoelectric strain constant and a large specific resistance, it is extremely useful as a material for an actuator, particularly a laminated piezoelectric element.

[Brief description of drawings]

FIG. 1 is a main component (Pb (Ni _1/3 N
b _2/3) O ₃ shows the composition range of -PbTiO ₃ -PbZrO _3).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 41/187

Claims (2)

[Claims] 1. The general formula (1-w) {xPb (Ni _1/3 Nb _2/3 ) O.
_{3 -yPbTiO 3 -zPbZrO 3} -wPb (} Me 1/2 W
_1/2 ) O ₃ (x + y + z = 1), and the mixing ratio x, y, z is
In the composition chart, the following composition points A: (X = 0.74, y = 0.
25, z = .001) B: (x = 0.40, y = 0.59, z = 0.01) C:
(X = 0.40, y = 0.25, z = 0.35) D: (x = 0.06, y = 0.59,
z = 0.35) on the line connecting them and the composition range surrounded by this line, w is in the range of 0.001 ≦ w ≦ 0.2, and Me is N.
i, Mg, Cu, Zn or Co, and at least one of Mn, Cr and Fe is Mn.
In terms of _{O 2, Cr 2 O 3,} Fe 2 O 3, 0.005~
A piezoelectric ceramic composition containing 1.0% by weight. 2. Part of Pb is 0.001 to 0.2 C
The piezoelectric ceramic composition according to claim 1, which is substituted with at least one of a, Ba, and Sr.