JPS6333311B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a piezoelectric ceramic material used in an acoustic signal transducer for a marine measurement system. When transmitting and receiving acoustic signals using a marine acoustic measurement system, it is necessary to transmit and receive signal amplitude and phase information. Therefore, it is desired that the transducer used here has good wave transmission/reception sensitivity, can be driven with a large amplitude, and has a low directivity subpole. Conventionally, for this type of application, a thickness vibrator made of plate-shaped zircon-lead titanate-based piezoelectric porcelain has been used. However, in a vibrator made of such a material, the longitudinal vibration transverse effect is strongly excited in the frequency range below the resonant frequency of the thickness direction vibration, so the frequency characteristics of the transmitting and receiving sensitivity become extremely complex in this region. At the same time, since the acoustic radiation surface does not make a piston movement, the directional sub-pole becomes extremely large at frequencies other than thickness resonance. In addition, the dielectric constant ε ^T ₃₃ and the dielectric loss
Since the value of tan δ increases rapidly at a relatively low electric field strength, it also has the disadvantage that it cannot be driven with a large amplitude by applying a high electric field. An object of the present invention is to suppress the vibration of the longitudinal vibration transverse effect system in a region below the thickness vibration resonance frequency in a plate-shaped thickness direction vibrator polarized in the thickness direction,
Moreover, by providing a material that exhibits relatively small values of ε ^T ₃₃ and tan δ even when a high electric field is applied, the above-mentioned drawbacks of the conventional vibrator can be eliminated, and the directivity subpole is small and the large vibration An object of the present invention is to provide an acoustic signal transducer for a marine acoustic measurement system that can excite width vibrations. The material of the present invention is Pb _1-x Sr _x Ti _1-y (Mn _1/3 Sb _2/3 ) _y O ₃
It is a piezoelectric ceramic material with a composition expressed by: If the material of the present invention is applied to an acoustic signal transducer for a marine acoustic measurement system, a high-performance transducer with low directivity subpole and excellent phase characteristics and amplitude characteristics capable of large amplitude drive can be realized. . The details of the present invention will be explained below along with examples. Example 1 Starting materials for obtaining the material of the present invention include lead oxide (PbO), titanium oxide (TiO ₂ ), strontium carbonate (SrCO ₃ ), manganese carbonate (MnCO ₃ ), antimony oxide (Sb ₂ O ₃ ), Each powder was used. here,
SrCO ₃ and MnCo ₃ were converted into SrO and MnO, respectively, to obtain the required amounts. A predetermined amount of each powder was weighed, mixed in a ball mill using pure water, and the mixed powder was prefired at 850° C. for 1 hour. After crushing, 700Kg/cm ²
Pressure mold the powder at a pressure of 1,240℃ to 1,300℃.
After sintering for a period of time, it was processed into a rectangular plate shape of 23 x 23 x 5.5 mm. Burn silver electrodes on both sides and heat at 120℃.
A DC bias electric field of 8 kV/mm was applied for 1 hour to piezoelectrically activate it. After leaving it at room temperature for 24 hours,
Free admittance characteristics were evaluated using a vector impedance meter. _{Figure 1 shows x = _ _}
0.03 and y=0.05 are chosen as representative examples, and their free admittance characteristics are shown. It is clear that strong thickness vibrations are excited at about 350 KHz, and almost no vibrations are excited in the frequency range below that, which is a fully satisfactory condition. For reference, Figure 2 shows the free admittance characteristics of a typical zircon-lead titanate piezoelectric ceramic. The dimensions of this vibrator made of conventional material are the same as those shown in FIG. 1 above. In the vibrator made of this conventional material, many strong vibrations other than the thickness vibration are excited in a frequency range lower than the resonant frequency of the thickness vibration, and the condition is not satisfactory. As is clear from this example, if a thickness longitudinal vibrator is constructed using the piezoelectric ceramic of the present invention, it becomes possible to excite almost only thickness longitudinal vibration over a wide frequency range, and frequencies below the thickness resonance frequency can be excited. It is possible to keep the directivity sub-pole low even in the area. Example 2 The same method as described in Example 1 was used to make a 16 mm diameter
A 0.5 mm disk was prototyped, and after applying silver electrodes on the top and bottom surfaces and polarizing it in the thickness direction, we investigated the dielectric constant ε ^T ₃₃ , the dielectric loss tan δ, the electric field strength dependence of these constants, and the thickness longitudinal vibration electromechanical coupling. The coefficient _kt was measured. When the composition of the material of the present invention is expressed by the following formula Pb _1-x Sr _x Ti _1-y (Mn _1/3 Sb _2/3 ) _y O ₃ , the composition in the shaded area in Fig. 3 is formed by molding and sintering. This indicates that either a solid body cannot be obtained or the electric resistance is low, so that polarization cannot be performed by applying a DC bias electric field for a long period of time. For the compositions in the non-shaded areas in FIG. 3, a shaped sintered body was obtained, and the compositions could be subjected to polarization treatment, and exhibited great piezoelectricity after polarization. Representative examples of the results obtained are shown below. Figures 4a and b show the dependence of the dielectric constant ε ^T ₃₃ and the dielectric loss tan δ on the measured electric field strength, respectively, measured at a frequency of 1 kHz, and the dielectric constant is based on the measured value in an electric field of 50 V/cm. The dielectric loss is shown as a rate of change, and the dielectric loss is shown as an absolute value. In the figure, 1 is a representative example of materials according to the present invention: Pb _0.95 Sr _0.05 Ti _0.95
The characteristics of (Mn _1/3 Sb _2/3 ) _0.05 O ₃ are shown, and 2 shows the characteristics of G-1408 manufactured by Garson Co., Ltd. in the United States, which is commercially available as a material for high-output sonar.
It is clear that the material of the present invention has a smaller dependence on the applied electric field strength in both dielectric constant and tan δ, and can withstand high electric field driving. Furthermore, since materials exhibiting piezoelectricity similar to the material of the present invention have been reported recently, the electric field strength dependence of the dielectric constant and tan δ of these and the material of the present invention was also compared. 3 in Figure 4 is 0.965PbTiO ₃ +0.025LaO _3/2
+0.010MnO ₂ , 4 is Pb _0.93 Sr _0.07 Ti _0.96 (Co _1/2 W _1/2 )
The test results for materials expressed by _0.04 O ₃ are shown, and it is clear that both have greater electric field dependence than the materials of the present invention. The following table shows the dependence of dielectric constant on electric field (measured value in electric field of 50 V/cm is taken as reference, and is shown as the rate of change of the measured value at 10 kV/cm), and the absolute dielectric loss tan δ for the material of the present invention. value (however
It is shown as a value of 10kV/cm. ), and the electromechanical coupling coefficient k _t of vibration in the thickness direction. From these results, as mentioned earlier, the materials of the present invention have smaller electric field dependence of permittivity and tanδ than existing materials, and are suitable for thick vibrator materials for large amplitude drives. That is clear.

【table】

[Table] Items marked with * are conventional examples shown for reference, and their compositions and names are as stated in the notes column.
As is clear from Examples 1 and 2 above, the composition of the present invention suppresses vibrations in different modes in the frequency range below thickness resonance, so it is possible to excite pure thickness vibrations over a wide frequency range. I can do it. Therefore, the directivity sub-pole can be kept low for acoustic signal transmission. Furthermore, even when a high electric field electric signal is input, the rate of increase in dielectric constant and tan δ is small compared to existing materials. Therefore, if the material of the present invention is applied to an acoustic transducer material for an oceanographic measurement system, it will be possible to provide an excellent transducer.

[Brief explanation of the drawing]

FIG. 1 shows a typical example of the free admittance characteristics of the material of the present invention. The material composition is
The vibrator is _{a rectangular} plate with dimensions _of 23 x ₂₃ x _5.5 mm _, and is _polarized in the thickness direction. FIG. 2 shows the free admittance characteristics of a conventional zirconium titanate-based piezoelectric plate. The dimensions are the same as the vibrator shown in FIG. Figure 3 shows the material composition of the present invention.
When expressed as Pb _1-x Sr _x Ti _1-y (Mn _1/3 Sb _2/3 ) _y O ₃ ,
It shows the relationship between x, y values and material properties.
The shaded area in the figure indicates that either a molded sintered body cannot be obtained or the electrical resistance is so low that it is impossible to activate it by polarization treatment. Figures 4a and 4b show the measured values of the dependence of the dielectric constant and tanδ on the applied electric field strength, respectively, and the dielectric constant is
It is expressed as a rate of change from a measured value at an electric field strength of 50 V/cm as a reference, and tan δ is expressed as an absolute value. In the figure, 1 is shown as a representative example of the composition of the present invention (Pb _0.95 Sr _0.05 Ti _0.95 (Mn _1/3 Sb _2/3 ) _0.05
This data was obtained from O ₃ ). 2 is data obtained from G-1408 manufactured by Galton, USA, shown for reference. 3 is also one of the conventional examples.
This is data obtained from 0.965PbTiO ₃ +0.025LaO _3/2 +0.010MnO ₂ , and 4 is also one of the conventional examples.
Data obtained from Pb _0.93 Sr _0.07 Ti _0.96 (Co _1/2 W _1/2 ) _0.04 O ₃ are shown. It can be seen that the piezoelectric ceramic of the present invention exhibits sufficiently satisfactory values in all of these data.

Claims (1)

[Claims] When expressed as 1 Pb _1-x Sr _x Ti _1-y (Mn _1/3 Sb _2/3 ) _y O ₃ , the values of x and y are 0.009≦x≦0.16 0.015≦y≦0.12 A piezoelectric porcelain characterized by being within a composition range surrounded by a composition ratio having a value of.