JPH03215357A - Piezoelectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide a composition having high heat resistance and small change with the passage of time in resonance frequency by specifying each oxide composition ratio of components in a ceramic composition consisting of solid solution of PbO-NiO-Yb2O3-Nb2O5-TiO2-ZrO2. CONSTITUTION:The objective piezoelectric ceramic composition consisting of 64.59-69.97wt.% PbO, 0.07-1.56wt.% NiO, 0.29-5.99wt.% Yb2O3, 0.47-9.24wt.% Nb2O5, 4.62-15.02wt.% TiO2 and 7.35-22.38wt.% ZrO2. The composition has high heat resistance and small change with the passage of time in resonance frequency. In the above-mentioned composition, if each weight ratio of PbO, NiO, Yb2O3, Nb2O5, TiO2 and ZrO2 is out of the above-mentioned range, heat resistance becomes low and piezoelectric deterioration starts from a temp. >=100 deg.C lower when heated with soldering, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to a piezoelectric ceramic composition, particularly used for ceramic filters, ceramic oscillators, ceramic discriminators, surface acoustic wave elements, etc.
Concerning piezoelectric porcelain compositions. (Prior Art) Conventionally, piezoelectric ceramic compositions include P b T i O , P
Biz O3. to the binary system of bZr03. Crz Ch
+MnO. Attempts have been made to improve the piezoelectric properties by adding additives such as , ZnO, and the like.

Furthermore, PbTiOz PbZrO+ Pb (M
n l/3 N b! /3) 03 series and Pb
TiO, PbZr03 Pb (Mg+zs Nbz
is ) ternary piezoelectric ceramic compositions such as 03 series,
being developed.

In addition, in Special Publication No. 1979-37907, Pb(Njl/
3 Nbzz+ )03 PbTiOz PbZr0
Three series of piezoelectric ceramic compositions are disclosed.

(Problems to be Solved by the Invention) However, such conventional piezoelectric ceramic compositions have major problems in heat resistance, resonant frequency change characteristics over time, and the like.

As a conventional example, for example, P b ((M g l/3
Nb2/s) o. otT j o. stZ r
11.4 &} As shown by the broken line in the graph of Figure 1, the heat resistance properties of Os are shown by the broken line in the graph of Figure 1. When a conventional piezoelectric porcelain composition is heated, the temperature gradually decreases from about 100 degrees Celsius or more below the Chierie point. depolarization due to heat occurs, and the piezoelectric properties begin to deteriorate.

For this reason, the upper limit temperature for use of the piezoelectric porcelain composition is limited to around 200° C., which is far below the Curie point. The reasons for this are that the Curie point is lowered by solid solution of the third component and that the piezoelectric ceramic composition is inherently prone to depolarization.

On the other hand, in recent years, electronic components have become more and more chip-based, and chip elements such as small piezoelectric elements that can be surface mounted, such as ceramic filters, ceramic oscillator discriminators, and traps, have been developed. With conventional resin molded elements with leads or elements sealed in metal cases, the temperature rise of the piezoelectric ceramic socket during soldering is suppressed to about 200°C. It is also exposed to high temperatures of around 300°C.

Therefore, with conventional piezoelectric ceramic compositions, it is impossible to produce chip components that are heat resistant and highly reliable.

In addition, the time-dependent change characteristics of the resonant frequency of the conventional example described above are
As shown by the broken line in the graph of the figure, conventional piezoelectric ceramic compositions also had a major problem in the change in resonance frequency over time. In Figure 2, the elapsed time after the piezoelectric ceramic was polarized is shown on a logarithmic scale on the horizontal axis, and the rate of change in the resonance frequency is shown on the vertical axis. As can be seen from this example, the conventional piezoelectric ceramic composition shows a change over time of about 0.5%/time decade. This phenomenon is a serious problem because the frequency of the filter or oscillator changes significantly from its initial value after it is processed into a filter or oscillator.

Therefore, the main purpose of this invention is to have high heat resistance and
Moreover, it is an object of the present invention to provide a piezoelectric ceramic composition whose resonance frequency changes little over time.

(Means for Solving the Problems) This invention provides P b O N i O Y b!
In a ceramic composition consisting of a solid solution of 03Nbz Os TiOg ZrOz, the weight ratio (weight %) of each oxide constituting the ceramic composition is such that pbo is 6459.
~69.97, NiO is 0.07~1.56, ybto
s is 0.29 to 5.99, Nb, 05 is 0.47 to 9
．． 24, a piezoelectric ceramic composition having T i O z of 4.62 to 15.02 and ZrOt of 7.35 to 22.38.

(Effects of the Invention) According to the present invention, a piezoelectric ceramic composition having high heat resistance and a small change in resonance frequency over time can be obtained.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Example) First, PbO. Nip,Yb,03,
NbtOs. T i Ox and ZrO. These powders were weighed to have the composition shown in Table 1. After wet mixing and drying this raw material powder,
Calcined at 00℃. Next, an organic binder was added, wet-pulverized and sized, and then molded at a molding pressure It/1 to obtain a molded product. Then, the molded body was fired at 1000 to 1250°C to obtain porcelain. Baked electrodes were formed on both main surfaces of the obtained porcelain, and a voltage of 2 to 3 KV was applied in insulating oil at 50 to 80°C.
/Tsuru voltage for 30 minutes to obtain a piezoelectric ceramic composition.

The dielectric constant (
εr), radial electromechanical coupling coefficient (Kp), mechanical quality coefficient (Qm), and heat resistance temperature (°C) were measured. Table 2 shows the measurement results. The piezoelectric characteristics were determined by measuring the resonant frequency and anti-resonant frequency using an impedance measuring device and calculating from these measured values. Moreover, the heat-resistant temperature is the highest temperature among the temperatures at which the value of the electromechanical coupling coefficient is 90% or more of the initial value when the sample is held for 3 minutes.

Next, based on Tables 1 and 2, the reasons for limiting the composition of the present invention will be explained. ■If PbO is less than 64.59% by weight or 69.97% by weight, the heat resistance temperature will be low, and when heated by soldering etc., the piezoelectric properties will deteriorate from a temperature lower than 100'e. (See sample numbers 2 and 5). ■NiO is less than 0.07% by weight or 1.56% by weight
This is because if the temperature exceeds 100°C, the heat resistance is low, and when heated by soldering or the like, the piezoelectric properties deteriorate from a temperature lower than 100'C (see sample numbers 6 and 9).

■When Yb,o, is less than 0.29% by weight or exceeds 5.99% by weight, the heat resistance is low, and when heated by soldering etc., the piezoelectric properties deteriorate from a temperature lower than 100°C. Yes (see sample numbers 10 and 13).

■If Nb and oS are less than 0.47% by weight or more than 9.24% by weight, the heat resistance is low, and when heated by soldering etc., the piezoelectric properties will deteriorate from temperatures as low as 100°C or more. (See sample numbers 14 and 17). ■T i O. is less than 4.62% by weight or 15.0
This is because if it exceeds 2% by weight, the heat resistance is low, and when heated by soldering etc., the piezoelectric properties deteriorate from a temperature lower than 100°C (sample numbers 18 and 2).
(see 1).

■If ZrOz is less than 7.35% by weight or exceeds 22.33% by weight, the heat resistance is low, and when heated by soldering etc., the piezoelectric properties will deteriorate from a temperature lower than 100°C (sample 22 and 25).

In addition, the heat resistance characteristics and the time-dependent change characteristics of the resonant frequency of sample number 1 as an example of the present invention are shown in FIGS. 1 and 2.
Each is indicated by a solid line in the graph of the figure.

In the embodiment within the scope of the present invention, the Curie point is approximately 350°C, which is higher than that of the conventional example, and as is clear from the graph in FIG. 1, the electromechanical coupling coefficient significantly deteriorates to just below the Curie point. It can be seen that it exhibits high heat resistance without any problems.

Moreover, as is clear from the graph in FIG. 2, in the embodiment within the scope of the present invention, the change in resonance frequency over time is less than 0.1%/time decade, which is smaller than the conventional example, and a highly stable piezoelectric element is manufactured. You can see that you can get it. As described above, according to the present invention, a piezoelectric ceramic composition having high heat resistance and small change over time can be obtained.

[Brief explanation of drawings]

FIG. 1 is a graph showing the heat resistance characteristics of an embodiment of the present invention and a conventional example. FIG. 2 is a graph showing the temporal change characteristics of the resonant frequency of an embodiment of the present invention and a conventional example.

Claims (1)

[Claims] PbO-NiO-Yb_2O_3-Nb_2O_5-
In a ceramic composition consisting of a solid solution of TiO_2-ZrO_2, the composition weight ratio of each oxide (
weight%) is 64.59 to 69.97 for PbO, 0.07 to 1.56 for NiO, 0.29 to 5.99 for Yb_2O_3, 0.47 to 9.24 for Nb_2O_5, and 4.62 to 4.62 for TiO_2. 15.02, and ZrO_2
7.35 to 22.38.