LiNbO3-based sol-gel composite ultrasonic transducer poled at low temperatures

Abstract

Abstract A LiNbO3 (LN) based sol-gel composite could be suitable for high temperature ultrasonic transducer application at 700 °C, however, poling requires high temperature above 550 °C and it shows relatively low signal strength. In order to realize the polarization temperature reduction of an LN-based sol-gel composite ultrasonic transducer, alumina (AO) and strontium doped titanium oxide (TO) were chosen as sol-gel phase material, and LN/AO and LN/TO films were fabricated onto Inconel substrates. In each polling process, corona discharge after heat treatment in the furnace at 400 °C and at 200 °C was executed for LN/AO and LN/TO, respectively. Ultrasonic measurements up to 700 °C were performed and both transducers were able to confirm the reflected echoes and ultrasonic performance stability at 700 °C. Especially LN/TO showed the highest signal strength compared to previously developed high temperature lead-free sol-gel composite materials, Bi4Ti3O12 (BiT)/BiT and CaBi2Ta2O9 (CBTa)/BiT.