Energy trapping characteristics of bismuth layer structured compound CaBi4Ti4O15

Piezoelectric characteristics of bismuth layer structured compound CaBi4Ti4 O15 ceramics were studied in terms of the energy trapping phenomenon of the second harmonic thickness extensional (TE2) vibration mode. An electrode-b uried-type resonator was prepared by the co-firing technique to generate th e TE2 mode, and frequency-lowering-type energy trapping was realized. Favor able resonant characteristics were obtained for piezoelectric filter and os cillator applications with narrow frequency tolerances, which require a sma ll electromechanical coupling coefficient and a high mechanical quality fac tor. The electromechanical coupling coefficient for the TE2 vibration mode of the resonator was 13.9% and the mechanical quality factor Q(m) was 2560. The temperature coefficient of the resonance frequency was adequate for th e applications. The microstructure of CaBi4Ti4O15 ceramic was also investig ated. Marked shape anisotropy of the grain was observed, however, preferent ial grain orientation was not recognized when the ceramic was prepared by t he ordinary firing process.