JPS5938754B2 - piezoelectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric ceramic composition, particularly to a piezoelectric ceramic composition with excellent piezoelectric properties that can be used for powerful ultrasonic vibrators, piezoelectric transformers, speakers, and the like.

Traditionally, piezoelectric ceramic materials include barium titanate porcelain, lead zirconate titanate porcelain, magnesium niobate titanate lead zirconate porcelain, and zinc niobate silver niobate titanate zirconate lead porcelain, depending on the intended use. Various improvements have been made accordingly.

Although each of the above compositions has its own characteristics, it still has various drawbacks. That is, the conventional compositions had a drawback in that the value of internal stress at which the piezoelectric properties began to deteriorate was relatively small. The present invention eliminates the drawbacks of the above conventional compositions,
The present invention provides a piezoelectric ceramic composition with extremely excellent properties. This piezoelectric ceramic composition has Pb(ZnL/!Nb
”)A(LiV4Nb0)BTi♂rl)Os (however, 0<□0.50, 0<B≦0.25, 0.25□≦0
．． 625, 0.20≦D≦0.625, A+B+C+D
=1, including a composition in which 15% or less of Pb atoms are replaced with one or more of Br3Ca and Ba.

), manganese dioxide (0.05 to 5% by weight of the total amount of MnO2
2O3) It is a composition containing 0.03 to 2% by weight of the total amount, and has a large electromechanical coupling coefficient and a large mechanical quality factor, and also has a high linearity of resonance frequency and resonance resistance with respect to internal stress. It has characteristics such as excellent The characteristics that piezoelectric ceramics should have differ depending on their use.

For example, applications such as vibrators for generating powerful ultrasonic waves and piezoelectric transformers require large electromechanical coupling coefficients and mechanical quality factors, as well as excellent linearity of resonance frequency and resonance resistance with respect to internal stress. be done. The piezoelectric ceramic composition of the present invention is suitable for such uses. The present invention will be described below based on examples. The raw materials were weighed so as to have the composition shown in the table below, and the mixture was calcined at about 850° C. for 2 hours and then wet-pulverized in a ball mill.

After drying the crushed material, it is pressed to a pressure of approximately 700KT to create 20 pieces in diameter and 2WI in thickness! It was molded into a disk shape of 1,200° C. and baked at 1,200 to 1,310° C. for about 45 minutes. To measure piezoelectricity, fired porcelain is polished to a thickness of about 1wn, silver electrodes are baked on both sides, and then placed in silicone oil at 100-150°C at 3-4 KV/! The one polarized with a DC voltage of n was used. Furthermore, the linearity with respect to internal stress at resonance frequency 1 is approximately 12.5r for the above disk sample! Rln
A sample was cut into a rod shape of ×2rwL, and the transverse effect of this rod was measured and investigated. In addition, during the above process, MnO2
and Al2O, even if added when crushing the calcined product,
showed similar properties. In addition, as raw materials, PbO, Zn
O, Li2CO3, Nb2O,, TiO2, ZrO2,
MnO2, Al2O3, SrCO3, CaCO,,Ba
Although CO was used, there are no particular restrictions on the form of other materials, such as peroxides, hydroxides, and carbonates, as long as they become oxides during firing. The table below shows the characteristics of each sample.

In the table, A, B, C, D are Pb(Znl/3Nb2
/3) A(LlV4NbA)BTlcZrTP3 This is the ratio of each component in the basic composition.

Further, FR-T is expressed as a change in the resonance frequency when the maximum internal stress is 150!477f with respect to the resonance frequency when the maximum internal stress is several KVd. As is clear from the above table, the porcelain made of the composition of the present invention has MnO2
By adding and containing Al2O, the basic composition and the large coupling coefficient (which is the effect of adding MnO2) can be improved.
Kp) and mechanical quality factor (QM).
The linearity of the resonant frequency with respect to the internal stress is significantly improved, and the change in the resonant frequency when the maximum internal stress is 150 Kv/Cd becomes small. Therefore, the composition of the present invention is useful for applications such as powerful ultrasonic vibrators and piezoelectric transformers. It goes without saying that compositions other than those in the above-mentioned embodiments within the scope of the present invention also exhibit similar improvement effects. Poor, A>0.50, B>0.25, C<0.25, C
〉0.625, D〉0.20, D〉0.625 is difficult to sinter, or has low piezoelectricity (Kp is 0.15 or less),
Compositions in which the amount of Pb replaced by Sr, Ca, and Ba exceeds 15% have a significant decrease in piezoelectricity, and compositions in which the added content of MnO2 is less than 0.05% by weight have a small QM.
On the other hand, since it is difficult to sinter a composition exceeding 5% by weight,
The added content of Al, O, is less than 0.03% by weight and 2
Compositions exceeding % by weight have little effect on improving linearity with respect to internal stress at resonance frequency, and are therefore excluded from the scope of the present invention.

Claims (1)

[Claims] 1 Pb(Zn1/3Nb2/3)_A(Li1/4N
b3/4)_BTi_CZr_DO_3 (However, 0<
A≦0.50, 0<B≦0.25, 0.25≦0.62
5, 0.20≦D≦0.625, A+B+C+D=1)
The basic composition is a solid solution shown by , and manganese dioxide (MnO_2) is added as a subcomponent by 0.05 to 5 of the total amount.
A piezoelectric ceramic composition characterized in that it contains aluminum oxide in an amount of 0.03 to 2% by weight based on the total amount. 2 Pb(Zn1/3Nb2/3)_A(Li1/4N
b3/4)_BTi_CZr_DO_3 (However, 0<
A≦0.50, 0<B≦0.25, 0.25≦C≦0.
625, 0.25≦D≦0.625, A+B+C+D=
1. A composition in which 15% or less of Pb atoms are replaced with one or more of Sr, Ca, and Ba) is the basic composition, and the total amount of manganese dioxide (MnO_2) is added as a subcomponent. 1. A piezoelectric ceramic composition comprising 0.05 to 5% by weight of aluminum oxide and 0.03 to 2% by weight of aluminum oxide based on the total amount.