Fine-Tolerance Resonator Applications of Bismuth-Layer-Structured Ferroelectric Ceramics

Abstract

The two-layered SrBi2Nb2O9 (SBN) ceramic resonator that generates second harmonics of the thickness extensional vibration is a strong candidate for fine-tolerance-resonator applications, because of its small electromechanical coupling coefficient and high temperature stability. The Nd substitution of Sr in SBN is effective in further decreasing the temperature coefficient of resonance frequency (TCF) while maintaining its high maximum value of electrical quality factor (Qemax) at a resonance frequency. On the other hand, a grain-oriented SBN-type ceramic resonator has an attractive property of thickness shear vibration. The temperature coefficient of oscillation frequency (TCO) could be less than 10 ppm/°C in an ordinary oscillation circuit with grain-oriented SBN-type ceramics. In this paper, we describe how a fine tolerance resonator can be realized using compositional and structural designs of the bismuth-layer-structured ferroelectric (BLSF) ceramic resonator.