JPH0383859A - Piezoelectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain the title composition of piezoelectric porcelain capable of giving high stability, high radial electromechanical coupling coefficient and low specific dielectric constant by limiting a composition range containing Pb, Zn, Nb, Ti, Zr and O and by adding each specified amount of SiO2 and Al2O3 to the composition. CONSTITUTION:The objective composition can be obtained by adding 0.01-0.04wt.% of SiO2 and 0.1-0.5wt.% of Al2O3 to a composition of the formula (such a composition range as to contain the lines connecting the six points represented as (x+y+z)=1, and (a:x)=0.05, (y)=0.5, (z)=0.45, (b:x)=0.1, (y)=0.5, (z)=0.4, (c:x)=0.15, (y)=0.5, (z)=0.35, (d:x)=0.15, (y)=0.4, (z)=0.45, (e:x)=0.1, (y)=0.4, (z)=0.5, (f:x)=0.05, (y)=0.4, (z)=0.05 and to be surrounded by these six points). Using the present composition, piezoelectric porcelain having a radial electromechanical coupling coefficient of as high as >=55% and a specific dielectric constant of as low as <=1600 can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a piezoelectric ceramic composition used as an electromechanical energy converter such as a buzzer.

BACKGROUND OF THE INVENTION In recent years, speakers using piezoelectric ceramics are being applied to a wide range of fields. In particular, the application to telephones is rapidly becoming widespread, and when applied to telephones, it is necessary that the power consumption be low. Conventionally, this speaker or microphone ringer uses Pb (Mg1/3 Nb2/3)03 Pb.
TiO3-PbZr03 system or Pb (Zn1/3
Nb2/3)03-PbTi03-PbZr03-based piezoelectric ceramics have been used.

Problems to be Solved by the Invention Generally, in order to realize low power consumption of an element, it is necessary to keep the dielectric constant of the piezoelectric ceramic low. However, piezoelectric ceramics with conventional compositions have a high radial electromechanical coupling coefficient (kP) of 55% or more and a low dielectric constant (ε1/ε.) of 1650 or less. It is extremely difficult to obtain a high-quality ceramic with good reproducibility, and therefore porcelain with a relatively high dielectric constant has to be used.

Means for Solving the Problems In order to solve the above problems, the piezoelectric ceramic composition of the present invention comprises:
xPb (Mgl/3 Nb2/3)03-yPbT
iO3−zPbZroi <However, X+y+z=1
So, a: x=0.05. y=0.5, z
=0.45. b: x=L1, y=0.5,
z=0.4, c:x=0.15. y=0.5
, z=0.35. d: x==0.15°y=0.4, z=0.45. e: x=0.1
, y=0.4.

z=o, 5, f: x=0.05. y=0
．． 4, 5i02 is 0.0 in the composition range that includes the line connecting the six points of z = 0.55 and is surrounded by these six points.
1-0.04% by weight.

0.1 to 0.5% by weight of Al2O3 is added.

Function The piezoelectric ceramic composition described above has a high radial electromechanical coupling coefficient (k) of 55% or more and a low relative dielectric constant (εT/εO1) of 1600 or less. Obtainable.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

That is, the piezoelectric ceramic composition according to this example has xPb
(Znl/3 Nb2/3)03-yPbTio
3-zPbZroi (where x + y +
z=1, and a: x=0.05. y=0.
5, z=0.45. b: x=0.1, y
=o, s, z==0.4, c: x==0.
15. y=0.5, z=0.35. d: x
=0.15. y=0.4, z=0.45. e
: x-=0.1, y=0.4, z=0.5
, f :x=0.05. y=0.4, z=0.
0.01 to 0.04% by weight of Muko 5102 (composition range including the line connected by the six points of 55 and surrounded by these six points)
, 0.1 to 0.5% by weight of Al2O3 is added. The above composition range is indicated by the shaded area in FIG.

Next, the manufacturing procedure of the piezoelectric ceramic composition described above will be explained. First, PbO, TiO2, ZrO2.

ZnO, Nb205.5i02, and A1203 are weighed to have a predetermined composition and mixed in a ball mill.
This mixed powder is calcined at 800° C. and then ground in a ball mill. Then, 1000 kg/1000 kg of this pulverized powder
It is molded at a pressure of d and fired at a temperature of 1150 to 1200°C.

Table 1 shows the results of examining the electrical properties of samples with various composition ranges produced by such a method (however, for samples with headquarters added to the sample number, the results are shown in Table 1). Although it is outside the range, it is noted as a reference.) In order to investigate the electrical properties, the sintered body of each composition was polished and processed into a disk with a diameter of 16-1 and a thickness of 0.5 m. A-electrodes were baked on the upper and lower surfaces of the disk, and a DC electric field of 3 kv/IfI was applied for 30 minutes in silicone oil at 100° C., and the electrical characteristics were measured 24 to 36 hours later. Note that kP was calculated by measuring the resonance frequency and anti-resonance frequency using a commercially available impedance analyzer. At the same time, εO was calculated from the electric capacity of tZ (1k using the same measuring device). In addition, the value of X + yr z in Table 1 is xPb (Zn1
/3 Nb2/3 )037yTiO3-ZPbZr0
x, y when the composition is expressed in 3.

2, and x+y+z=1.

In addition, when x<0.05, sinterability deteriorates and the sintering temperature becomes high, resulting in increased evaporation of pbO during firing, which tends to cause variations in electrical properties during mass production. Industrially undesirable.

In addition, when x > 0.15, ε7/ε0 becomes large, and even if Al2O3 is further added to s i o2, 55
% or more, εT/ε of 1650 or less. It is difficult to produce with good stability while keeping the blade sharp.Furthermore,
If X≦0.15 and the composition is outside the range surrounded by a%f, kp will be less than 55%, making it unsuitable as an electromechanical transducer; on the other hand, if 5102 is less than 0.01% by weight, , when Al2O3 is less than 0.1% by weight, no addition effect is observed, and when 5102 is less than 0.1% by weight.
k if the amount of Al2O3 is more than 0.5% by weight.

is less than 55%, the decrease is significant, and it is not suitable as an electromechanical device.Additionally, adding 5102 or Al2O3 alone does not have sufficient effect, so it is necessary to add both.

Effects of the Invention As described above, according to the piezoelectric ceramic composition of the present invention, a composition having a small relative dielectric constant and a high radial electromechanical coupling coefficient can be obtained, and therefore a highly efficient electromechanical transducer with low power consumption can be obtained. can be obtained with good stability.

[Brief explanation of drawings]

FIG. 1 is a composition diagram of the piezoelectric ceramic composition of the present invention.

Claims (1)

[Claims] 1, xPb(Zn1/3Nb2/3)O_3-yPbT
iO_3-zPbZrO_3 (x+y+z=1
And a: x=0.05, y=0.5, z=0.45
, b:x=0.1, y=0.5, z=0.4, c:x=
0.15, y=0.5, z=0.35, d:x=0.1
5, y=0.4, z=0.45, e:x=0.1, y=
0.4, z=0.5, f:x=0.05, y=0.4,
SiO_2 is added from 0.01 to 0.0 in the composition range (including the line connecting the six points of z=0.55 and surrounded by these six points).
4% by weight, and a piezoelectric ceramic composition containing 0.1 to 0.5% by weight of Al_2O_3.