Piezoelectric properties in textured ceramics of bismuth layer-structured ferroelectrics

Piezoelectric properties and their temperature stability were studied for the <001> textured ceramics of bismuth layer structured ferroelectrics SrBi2Nb2O9 (SBN) type compound. The <001> textured ceramics of 10% Nd substituted SBN were obtained by the templated grain growth (TGG) method, and the orientation degree reached 96%. Electro-mechanical coupling coefficient of thickness shear vibration for the 96%-textured specimen was three times larger than that for the randomly oriented specimen. In addition, the resonance frequency increased with increasing temperature for the 96%-textured specimen, while it decreased for the randomly oriented specimen. Therefore, textured ceramics with various orientation degrees were prepared. The gradient of the temperature variation in the resonance frequency changed from negative to positive with increasing grain orientation, and an excellent temperature coefficient of resonance frequency (TCF) of −0.4 ppm/°C was obtained for the specimen with 76% orientation. Moreover, the specimens with the major faces formed at various angles to <001> oriented direction were fabricated from a 96%-textured ceramics. The gradient of temperature variation in resonance frequency changed from negative to positive with decreasing angle. the minimum value of TCF was −2.6 ppm/°C for the specimen with a 30° angle. Optimization of the orientation degree or the major face angle was effective to improve TCF for thickness shear vibration of SBN type ceramics.