Acoustic Wave Characteristics of Lead-Free (Bi1/2Na1/2)0.99Ca0.01TiO3 Piezoelectric Ceramic

Abstract

Acoustic wave characteristics of lead-free (Bi_1/2Na_1/2)_0.99Ca_0.01TiO₃ (BNC-1) piezoelectric ceramic are studied from a viewpoint of a new substrate material group for a surface acoustic wave and/or a bulk acoustic wave. The BNC-1 ceramic, which has high electromechanical coupling factors, k ₃₃(=37.6%) and k _t(=51.3%), and low free permittivities, ε ₃₃ ^T/ε ₀(=236) and ε ₁₁ ^T/ε ₀(=271), along with a high mechanical strength, is favorable to high frequency ultrasonic uses. Two interdigital transducers can excite an SH plate mode wave or a Lamb mode wave whose travelling direction is perpendicular or parallel to the poling axis, respectively. A delay line type oscillator using the SH wave is demonstrated a single mode oscillation of 8.319 MHz.