Development of A High-temperature Piezoelectric Ultrasonic Transducer Based on a Glass Substrate

Abstract

The piezoelectric ultrasonic transducer is a key device in ultrasonic applications. In oil logging, the bottom-hole temperature increases with the drilling depth. With the rapid increase of deep and ultra-deep well exploration, the bottom-hole temperature can reach 175°C or even higher, so new requirements are made for the stability of piezoelectric ultrasonic transducers for logging to work in such high-temperature environments. In this paper, a high-temperature piezoelectric ultrasonic transducer (HT-PUT) based on the high-temperature glass substrate has been developed and characterized in detail. After HT-PUT device fabrication and electromechanical experimental tests, it is shown that both the resonant frequency curve and the effective electromechanical coupling coefficient can be regulated and optimized by changing the size of the through-hole cavity in the glass substrate. After designing an appropriate through-hole cavity, the effective electromechanical coupling coefficient of the HT-PUT in the thickness-extensional mode can be significantly improved by 64.9%. The HT-PUT was tested in the temperature range of 25 °C to 250 °C, and its resonant frequency was only shifted down by 3.2%. This work demonstrates a high-temperature glass-based piezoelectric ultrasonic transducer that can operate in harsh conditions above 250°C, such as oil and gas exploration applications.