Lithium niobate piezocomposite phased arrays operating at high temperatures

Phased arrays made from high-temperature-resistant piezocomposite have been investigated for non-destructive testing. The piezocomposite material was made from lithium niobate in the 1–3 connectivity (pillar) configuration, manufactured by the dice-and-fill method using high-temperature cement as the passive matrix.

Lithium niobate piezocomposites were used in ultrasonic measurements at high temperatures. In transmit/receive tests on a steel test block, clear back-wall echoes were seen at temperatures up to 500°C and the piezocomposite material remained operational after returning to room temperature. In phased array tests using an RD Tech array controller, an eight-element lithium niobate piezocomposite array with element width 1 mm and inter-element spacing 1.5 mm was able to detect a side-drilled hole representing a defect at 300°C.

Lithium niobate is an important piezoelectric material for high-temperature ultrasonic applications since it is cheap and widely available and has a very high Curie temperature of 1210°C. The benefits of using piezocomposite rather than single-crystal plates of lithium niobate were increased robustness of the active material under thermal cycling, reduced lateral modes, and increased electromechanical coupling coefficient, kt.