Properties of niobate high-temperature piezo-electric ceramics

Piezo-electric ceramics based on barium titanate have found applications in transducers for vibration measurement and in the generation and detection of ultrasonic vibration, where they combine low cost with properties more advantageous than those of piezo-electric crystals such as quartz, Rochelle salt or ammonium dihydrogen phosphate. Niobates have the further advantage that they retain their piezo-electric properties at temperatures considerably higher than the titanates. They are therefore suitable for use in vibration transducers able to operate at high temperatures and in ultrasonic generators able to operate at large amplitude, without losing their piezo-electric properties as a result of overheating. Some of the materials have a low temperature coefficient of resonant frequency and may therefore find applications in composite resonators in filter circuits.