Preparation and characteristics of ultrasonic transducers for high temperature using PbNb2O6

The substance PZT(Pb(Zr, Ti)O-3) is chiefly used for piezoceramic transduce rs in many ultrasonic flow meters. It is difficult to use PZT transducers f or flow meters for automobile exhaust gas at high temperatures over 350 deg rees C. Lead niobate (PbNb2O6) has a high Curie temperature of 540 degrees C and a low mechanical quality factor, and is the most suitable as the sens or element in flow meters for automobile exhaust gas. However, it is diffic ult to fabricate dense PbNb2O6 ceramics that have good piezoelectric proper ties. In this study, ceramics with high density and a high piezoelectric ef fect were fabricated by adding various elements such as Mn and Ca to PbNb2O 6 and by examining the sintering process. A Langevin transducer with a reso nance frequency of 80 kHz was made for measuring automobile exhaust gas flo w using PbNb2O6 ceramics.