Response Optimization of LiNbO3 Ultrasonic Transducers for High Temperature Measurement

LiNbO3 thin-film ultrasonic transducers were deposited using the RF magnetron sputtering technique. Optimization of the sample position in the deposition chamber and deposition parameters was carried out to obtain the strongest pulse-echo response of LiNbO3 transducers. The position of the sample in a plane parallel to the target surface had a significant impact on the transducer morphology, which changed from a columnar structure to a layer with embedded wedges. An exponential correlation between the amplitude of the pulse-echo response and the transducer thickness was found. The structural quality of the transducer layer was the main factor influencing the response amplitude. A temperature sensor in the form of a thin film ultrasonic transducer deposited on a bolt cup was prepared. To measure temperature, a linear dependence between longitudinal wave time-of-flight and bolt temperature was used. The optimization of the response of the transducer allows for more accurate temperature measurements using higher-order pulse echoes.