JPS5947784A - Piezoelectric ceramic composition - Google Patents

Abstract

PURPOSE:To offer a piezoelectric ceramic composition which has the anisotropy of the coupling coefficient of electric machines at a low dielectric constant and has the coupling coefficient of electric machines by thickness vertical oscillation larger than that of PbTiO3 by a method wherein the composition is composed of a solid solution of two components of xPbZrO3-yPb(Mn1/2Nb1/2)O3(x+y=1.00) and a solid solution of three components of xPbZrO3-yPb(Mn1/2Nb1/2)O3-zPbTiO3 (x+y+z=1.00), and the mixture ratio (x) of the PbZrO3 is contained by 0.9 or more. CONSTITUTION:The range of composition of the ceramic is within the range expressed by x=0.905-0.960, y=0.040-0.095 in the case of x+y=1.00 of the solid solution of the two components constituted by xPbZrO3-yPb(Mn1/2Nb1/2) O3. The raw material powder at a fixed ratio of composition is drymixed by means of a pot mill, and then provisory sintering is performed after drying. This provisory sintered body is mixed again by means of the pot mill after grinding by using an attrition machine. It is press-molded after resulting in sintering. This sintered body is cut to the thickness of approx. 1mm. and polished to the thickness of 0.8mm., then Cr-Au is vapor-deposited on both surfaces. Further, Cu lead wires are attached with Au paste, thus polarization treatment performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a piezoelectric ceramic used for ultrasonic vibrators, ceramic filters, and the like.

[Prior art]

Conventionally, as this type of piezoelectric ceramic, so-called PZT-based piezo porcelain and BaTiOs-based porcelain whose main components are zircon-lead titanate (PbZr03-PbTi03) have been used, but these porcelains inherently have a high dielectric constant. (1000~
3000) Since it is made of porcelain, the input/output impedance of the element decreases when used at high frequencies, resulting in the same order of impedance matching with the external circuit. Particularly recently, the frequency of piezoelectric elements has been increasing, and the dielectric constant is relatively small (approximately 200
) PbTi03-based porcelain is attracting attention. This PbTi
0. In addition to (1) a small dielectric constant, ceramics have (2) anisotropy of the electromechanical coupling coefficient, that is, an extremely large electromechanical coupling coefficient ratio kt/kp of thickness longitudinal imaging and transverse vibration (kt /kp=10~15.PZ'l'' and BaTi0
8 porcelain k t/k p = 1~2), and (3)
Electromechanical coupling coefficient of thickness longitudinal vibration 1 (t is relatively large (
It is a very unique material with a pressure of 0.5), which is not found in any currently known porcelain. Therefore, many applied devices utilizing this unique characteristic have been put into practical use. For example, the large anisotropy of the electromechanical coupling coefficient of PbT10, a ceramic, has recently attracted attention as a piezoelectric ceramic for ultrasound probes used in medical ultrasound diagnostic devices and the like.

In other words, although the frequency of ultrasound diagnostic equipment is increasing,
When the frequency exceeds 5MI-TZ, it becomes difficult to fabricate the A1/A probe using conventional PZT piezoelectric ceramics. This is because the anisotropy of the electromechanical coupling coefficient of PZT-based porcelain is small, so there is a restriction that W'/l<1 on the ratio of the thickness and width of the elements constituting the array.

Therefore, recently, the electromechanical coupling coefficient kp of unnecessary lateral imaging, which causes this constraint, has been changed to that of the necessary thickness direction vibration kp.
PbTi0.t is small compared to t. Piezoelectric ceramics are attracting attention as materials for high-frequency probes. Until now, (Pb,
, Cax) ((CO+7t W+4)yT'+ -y
l) kp=0.05 for 03+MnQ porcelain. kt-
Materials with properties of 0.50 (kt/kp~10) have been developed and their usefulness has been demonstrated.

But 1. The detection sensitivity of probes using pbTio and thread porcelain is decreasing, and as the frequency becomes higher, the sensitivity decreases more and more. Therefore, increasing the detection sensitivity is a major challenge for high-frequency probe cores, and for this purpose,
・Well, the electromechanical coupling coefficient kt of thickness longitudinal vibration must be increased.

[Purpose of the invention]

The purpose of the present invention is to take the above-mentioned r'b'r;o, the unique characteristics of porcelain one step further, and to take PbTi0. Compared to porcelain, it has a low dielectric constant and large electromechanical coupling coefficient anisotropy, and the electromechanical coupling coefficient of thickness longitudinal vibration is P b 'l'
i'0. It is an object of the present invention to provide a composition for a larger piezoelectric device.

[Summary of the invention]

The piezoelectric ceramic composition of the present invention has X P b Z r O5
-yPb (11Jn+7t Nbt/i)o
A binary solid solution of s (x+y = 1, oo), and xI'bZrOs VPb(Mnl/
/! Nbl/2 ) Os-2P bTt Os (x
+ 'f + Z = 1.00), and the piezoelectric ceramic composition is characterized in that it is composed of a three-component solid solution of % P b Z r 03 and has a blending ratio X of 0.9 or more. This two-component and three-component solid solution piezoelectric ceramic composition is
It is already known as a piezoelectric porcelain that has a large mechanical quality factor and excellent temporal stability of the core frequency. However, these piezoelectric ceramics have a PbZrO3 blending ratio X of 0.
．． It is said that if the value is greater than 9, the stability deteriorates and the piezoelectricity deteriorates to the extent that it cannot be put into practical use.

The piezoelectric ceramic composition of the present invention has PbZr0. These piezoelectric ceramic compositions belong to a composition region with a blending ratio of 0.9 or more, and from a detailed study of the blending ratio and synthesis conditions, it was found that these piezoelectric ceramic compositions have extremely excellent piezoelectric properties. In particular, the anisotropy of the electromechanical coupling coefficient and the electromechanical coupling coefficient of longitudinal vibration are larger than those of pb'rio3, and the dielectric constant is also smaller.

In addition, the mechanical quality factor QM is also PbTi0. Because it is several times larger than the conventional ultrasonic transducer, it can be used as an excellent ultrasonic transducer or filter material that can withstand use at high frequencies.

Expressing in more detail the composition range of porcelain that exhibits the above-mentioned excellent properties, we get xP bZ rQ3 yP b <Mnl
72N b + 7t ) Of the two-component solid solution composed of Os, when x + y = 1.00, x = 0.905
~0.960. It falls within the composition range expressed as y=o, o4o~0.095. Within this composition range,
The piezoelectric ceramic composition has a small dielectric constant and a large anisotropy of electrical mechanical coupling coefficient and a large electromechanical coupling coefficient of longitudinal thickness vibration.

If the blending ratio of PbZrO3 is higher than this composition range, the resulting porcelain becomes an antiferroelectric material and cannot normally be used as a piezoelectric ceramic. Furthermore, when the blending ratio of PbZrO3 is small, the dielectric constant becomes large and the anisotropy of the electromechanical coupling coefficient becomes small.

And xP bZrOs YP b (Mn+/z
Nbl/2) 03-ZPbTiO, among the three component solid solutions, x + y + Z = 1.
When OO, X, y, and z are each X Y Zff'9
05 0.095 0.0000.960
0.040 0.0000.932 0.0
05 0.0630.905 0.005
Within the composition range defined by the composition ratio expressed as 0.090, the dielectric constant and electromechanical coupling coefficient for lateral imaging are small;
The electromechanical coupling coefficient of thickness longitudinal vibration increases. In addition,
The piezoelectric ceramic composition also has good other piezoelectric properties.

PbZr0. If the compounding ratio exceeds the above-mentioned effective compounding ratio, the material becomes an antiferroelectric material and cannot normally be used as an IE electromagnetic device. Furthermore, if the blending ratio of Pb (Mn+7.Nb+/1)Us and Pb'['i03 is greater than the above-mentioned effective blending ratio, the mechanical quality factor and dielectric constant will increase. Further, the electromechanical coupling coefficient k p of lateral vibration becomes large, and the coupling coefficient ratio becomes small. Furthermore, P b (Mnt
/z N bt/l ) Os in a composition of 0.005 or less, that is, a composition close to that of conventionally known PZT porcelain, the PbO evaporates significantly during sintering, making it difficult to obtain stable porcelain. In addition, the electric resistance decreases, which makes the polarization process difficult and the characteristics not only become unstable, but also effectively decreases the electromechanical coupling coefficient of thickness longitudinal vibration.

Hereinafter, the present invention will be explained in detail with reference to Examples.

[Embodiments of the invention]

Example 1 Table 1 shows P bZ r Os P b (M, 'n+
, A Nb+7= ) Samples (1 to 7) regarding the Os two-component solid solution are shown together. As starting materials for obtaining the porcelain of the present invention, unless otherwise specified, lead oxide (1' b O) and zirconium oxide with a purity of 99.9% or more are used.
Powders of manganese oxide (MnO), manganese oxide (MnO), and niobium oxide (Nb, 0!l) were used.

Raw material powders having a composition ratio within the range shown in Table 1 were wet mixed for about 1 hour using a bot mill, and after drying, the mixture was heated to 9°C.

Temporary sintering was performed at C for 2 hours. This pre-sintered body was pulverized using a Raikai machine and then mixed again using a bot mill. After drying, it was press-molded at a pressure of 350 da/cm2.
Sintering was carried out at 1250 to 1280 t:' for 5 hours.

The size of the sintered body is 16φ×10w+m. This sintered body was cut to a thickness of about 1 m, polished to a thickness of 0.8+o+, and Cr-ALI was vapor-deposited as electrodes on both sides.

Furthermore, copper lead wires were attached using silver paste and polarized.

Polarization treatment is carried out in silicone oil at 70-150C.
This was carried out by applying a DC voltage of 0 to 50 kV/crn for 10 minutes. Thereafter, dielectric and piezoelectric properties were measured.

As is clear from Samples 1 to 4 in Table 1, the piezoelectric ceramic composition of the present invention has a small dielectric constant of 200 or less and a large anisotropy of electromechanical coupling coefficient of 10 or more. Furthermore, the electromechanical coupling coefficient kt of thickness longitudinal vibration is greater than that of the Pb'l'i03m device by 0.55 km (tb').

KR5 Oh! and 6id, Pb(Mnt/lNr/2)Os
If the blending ratio exceeds 0.10, in this case,
The dielectric constant becomes large, and the electromechanical coupling coefficient of transverse vibration also becomes large, and the anisotropy decreases.

Sample 7 has a blending ratio yjE O of P b Z r Os
. In addition, Example 2 of porcelain bonding which becomes an antiferroelectric material P bZ r Os P b (%In, /2N b
t7z) The excellent properties of the two-component solid solution of Os further include pbzro, which contains pb'rio, and Pb(M
n+/1! Nbl/2)03 Pbi'jOs is preserved even when formed in a three-component solid solution, and in addition, the mechanical quality factor increases.

The method for preparing the sample was the same as in Example 1.

Titanium oxide (Ti) is used as a starting material for titanium (Ti).
02) was used.

Samples 8 to 15 are shown together in Table 2. As is clear from each sample, the electromechanical coupling coefficient and mechanical quality factor are extremely large, and the dielectric constant is small in many compositions, and the electromechanical coupling coefficient of thickness longitudinal vibration is
ZrO3Pb(Mn,/2Nb, 7.) is improved from a binary solid solution.

If the blending ratio of PbZrO3 is lower than the effective composition ratio above, that is, P b (Mnt/z N1)t/
l) os and PbTi0. When the composition ratio is large, the dielectric constant becomes large and the anisotropy of the electromechanical coupling coefficient also becomes small.

Furthermore, if the blending ratio of PbZrOs is greater than the composition range of the present invention, it becomes an antiferroelectric material.

Finally, P b (Mn+/z N b1/2) Os
So-called 1) bZ rOs-p b
In 'l' ios porcelain, the electromechanical coupling coefficient of thickness longitudinal vibration becomes small.

〔Effect of the invention〕

As explained above, Xpbzro3-yPb(M”I
/2Nbl/2 )03 Behind the binary solid solution, x +
When y=1.00, x=0.905 to 0.960
．． A piezoelectric ceramic composition within the composition range expressed as y=0.040 to 0.095, and xPbZrO,yPb(M
nt/1Nbt, A) Us Zpb'rio3a component solid solution, x + y - t-z = 1. OO
Then, in the ternary composition diagram, X.

y and z are respectively x y zO
,,9050,0950,000 0,9600,0400,000 0,9320,0050,063 0,9050,0050,090 A piezoelectric ceramic composition within the composition range represented by Pb possesses piezoelectricity, has a particularly low dielectric constant, and has a large anisotropy in the electromechanical coupling coefficient, and the electromechanical coupling coefficient at thickness B is also significantly large.
Ti0. As an alternative to porcelain, it is clear that TC porcelain has unprecedented characteristics.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. xPbZr(Js yPb (Mn+/l
Among the binary solid solutions composed of Nbl/2)O3,
x+y=1. When oO, x = 0.905 to 0.
960. A piezoelectric ceramic composition characterized by having a composition within a composition range expressed as y=0,040 to 0.095. 2. xPbZros YPb(Mn+/zN
l)+/1)03-zpbTiQ, When x+y+Z=1.00, in the ternary composition diagram, x=0.905 y=0.095 z=o, ooo
Composition ratio expressed as: x=0.960 y=0.04o z=o,o
Composition ratio represented by oo, x=0.932 y=0.005 2=0.06
Composition ratio represented by 3 and x=o, 905 y=o, oo5 Z=0.0
A piezoelectric ceramic composition characterized in that the composition is within a composition range surrounded by a composition ratio represented by 90.