Deeply trapped electrons induced long-time sustainable mechanoluminescence of X-ray irradiated La2Ti2O7:Pr3+ for detection of stress burst

Abstract

X-ray irradiated La2Ti2O7:Pr3+ was found to show long-time sustainable mechanoluminescence (ML), which can realize the high sensitivity and real time detection of stress burst for more than 72 h. Under the excitation of X-ray, La2Ti2O7:Pr3+ shows red ML emissions located at 610, 624 and 638 nm, which are similar to the afterglow emission spectrum and can be ascribed to1D2-3H4, 3P0-3H4 and 3P0-3H2 of Pr3+. And the linear increases of compressive load can induce the linear increases of ML intensity of the sample, indicating that the X-ray induced ML emission can be utilized to accurately detect the stress applied on the object. Furthermore, X-ray irradiated La2Ti2O7:Pr3+ possesses excellent stability and the repeatability of ML emission and the ML signals can keep stable even 50 load cycles after 1 h decay. The thermoluminescence results suggest that abundant electrons are trapped in shallow and deep answered for stable ML emission. More importantly, the deeply trapped electrons induced ML emissions from X-ray irradiated La2Ti2O7:Pr3+ can be utilized to detect the stress bursts for a long time. When the sample is recharged by 5 min X-ray irradiation once, within 24 h decay, the 1500 N burst among many 1000 N cycles can be clearly detected, and the signal to noise ratio (S/N) reaches 1.32 and 1.26 after 12 and 24 h decay, respectively. And even after 72 h decay, the S/N of 2500 N still arrives at 1.23 and that of 4000 N reaches 1.97, indicative of long-time high sensitivity detection of abnormal stress. All these results suggest that the X-ray-irradiated La1.97Ti2O7:0.03Pr3+/resin sample can realize the high sensitivity and real time detection of stress burst for more than 72 h, which thus possesses great potential application in early warning of the emergency disasters such as bridge fracture, tunnel collapse and so on.