β-SiAlON phosphor-in-glass mechanoluminescent materials for high-frequency mechanical sensing

The mechanical sensing technology based on mechanoluminescence (ML) shows several advantages such as remote response, stress distribution visualization and self-powering emission, which is expected to bring a breakthrough in the field of mechanical sensing. However, slow response and poor thermal stability are two major challenges in the ML-based sensing technology. In this work, an all-inorganic ML material β-SiAlON@glass was prepared by combining β-SiAlON (Si6−zAlzOzN8−z:Eu2+) phosphors with a low-melting-point glass. The β-SiAlON@glass showed the shortest ML lifetime of 9.8 µs reported so far, which was mainly due to the d-f electronic transition of Eu2+, very little persistent luminescence, and the high elastic modulus of the glass matrix. The β-SiAlON@glass exhibited excellent thermal stability with ML lifetime and peak intensity unchanged at temperatures up to 400 K. We revealed that the self-recoverable ML in the β-SiAlON@glass was primarily attributed to the triboelectric effect. Finally, we applied the β-SiAlON@glass to fabricate a ML sensor with a response time of 29 µs, which could clearly detect high-frequency ultrasonic waves at 25 kHz. The above results cannot only help us to further understand the mechanism in ML materials, but also provide an useful guidance for the development of high-performance ML sensors.