High kt piezoelectric ceramics

The properties of modified lead titanate ceramics (Pb,La) (Ti,Mn)O ₃ doped with Cr₂O₃ are investigated. The dielectric constant increases with increasing addition of Cr₂ O₃, and the fundamental thickness coupling factor k _t does not show a large fluctuation. But the planar coupling factor shows a lower value for 0.4-0.8 wt.% additives. Meanwhile, at about 0.4 wt.% doping, the coupling factor k_t and the temperature coefficient of the third overtone thickness extension vibration mode have improved values of 0.3 and -6 p.p.m./°C, respectively. Thus the chromium addition may be considered as a promoter of stabilization in a certain range. The pure third overtone spectrum of the thickness mode can be strengthened by decreasing the electrode diameter, and the frequency constant reaches about 6820 kHz-mm