High-temperature thin film lithium niobium oxide transducers for bolts

In the present work, we studied structure, surface morphology, and ultrasonic response of thin film Lithium Niobium Oxide (LNO) transducers deposited on Inconel bolts, stainless steel and silicon substrates by radio frequency magnetron sputtering. The deposited transducer material was a mixture of LiNbO3/LiNb3O8 phases, having a well-developed columnar structure. Further, the in-situ high-temperature ultrasonic response was studied in the temperature range of 18-800 degrees C in ambient air during short-term annealing. It was observed that long-term annealing (at 700 degrees C for 160 h and 800 degrees C for 40 h) deteriorated the ultrasonic response, owing to the irreversible change from the initial columnar structure to the porous granular structure. Dielectric and piezo-electric properties of the thin film LNO transducers were also studied. The thin film LNO ultrasonic transducers have potential applications in bolts and screws up to 700 degrees C.