Preparation and acoustic properties of high-temperature acoustic emission sensor based on La3Ga5SiO14 crystal

With the rapid development of modern industries, the high-temperature piezoelectric sensors that can work in extreme environments are in great demand. In this work, langasite (La 3 Ga 5 SiO[Formula: see text], LGS), as a high-temperature piezoelectric crystal with stable electro-elastic performance, is used as core element, and air and porous Al 2 O 3 are selected as backing layers respectively to prepare two kinds of high-temperature acoustic emission (AE) sensors. The detection sensitivities at 25–500 ∘ C are analyzed by the ball falling test and Hsu–Nielsen experiment. Under the condition of 25–500 ∘ C, the received amplitude signals by both sensors are maintained above 90[Formula: see text]dB stimulated by the ZrO 2 ceramic ball dropping. In the Hsu–Nielsen experiment, as the temperature rising from 25 ∘ C to 500 ∘ C, the signal amplitude of sensor with air backing layer decays from 447[Formula: see text]mV to 365[Formula: see text]mV, while the signal amplitude varies from 270[Formula: see text]mV to 203[Formula: see text]mV for the sensor with porous Al 2 O 3 backing layer. Significantly, compared with the bandwidth of the air-backing sensor (37–183[Formula: see text]kHz), the sensor with porous Al 2 O 3 backing layer broadens bandwidth to 28–273[Formula: see text]kHz. These results show that both these AE sensors have strong and stable response ability to AE signals at high-temperature of 500 ∘ C. Therefore, piezoelectric AE sensor based on LGS has great potential application in the field of high-temperature structural health monitoring.