Keiichi Takahashi

Effect of Y and Mn Doping in Pb(T, Zr)O3 Piezoelectric Ceramics on the Resonant Frequency and Capacitance Changes and Aging by Thermal Shock Tests

The effects of Y and Mn-doping in Pb(Zr, Ti)O3 (PZT) with respect to the resonant frequency changes and the aging phenomena caused by thermal treatment were studied in order to achieve a stable piezoelectric ceramic filter. Good thermal stability as well as a high mechanical quality factor QM were required for the piezoelectric ceramics to fabricate certain types of narrow band monolithic filters. The Cr-doped PZT showed a little aging phenomena in resonant frequency change after thermal shock tests, but QM was not high. The Cr and Mn-doped PZT had a large QM value, but a large amount of resonant frequency change and aging after thermal shock tests. It was observed that the PZT with the addition of Y and Mn has high QM and good temperature stability. These features were suitable for the use in filters and resonators.

Piezoelectric Properties of Nanostructure-Controlled Lead-Perovskite-Based Ceramics

We studied the piezoelectric properties for structure-controlled ceramics of (Pb 0.9 Sr 0.1 )(Mg 1/3 Nb 2/3 ) 0.255 Ti 0.38 -Z 0.365 O 3 prepared by the ultrafine powder process called the «nanopowder process». The dense and uniform fine-grained ceramics in this system, which had the relative density of 97.5% and the average grain size of 1.9 μm, wire obtained by this process. The sample prepared by this process showed the large dielectric constant of above 5300 and the high electromechanical coupling factor k 31 of 0.41. It was found that, the nanopowder process is effective to improve the piezoelectric property. The maximum value of the piezoelectric constant |d 31 | was 356×10 -12 m/V