Visible to Near-Infrared Mechanoluminescence from Pr-Doped LiTaO3 for Stress-Sensing Applications

This study explores the mechanoluminescence (ML) properties of the LiTaO3 host material with a trigonal R3c structure with variable concentrations of praseodymium (Pr) activator ions (1% (S1), 3% (S2), and 5% (S3)). Three distinct ML experimental setups, namely, friction-induced mechanoluminescence (F-ML), impact-induced ML (I-ML), and stress-induced ML (S-ML), are utilized to examine their ML properties. F-ML measurements demonstrate the ML spectra of LiTaO3:Pr, which have emissions in green, red, and IR regions. I-ML measurements exhibit their fast detection capabilities of applied mechanical impact with excellent ML recoverability at various impact kinetic energies. S-ML experiments reveal a remarkable superposition of emitted ML intensity curves with the time-dependent applied force. Photoluminescence results exhibit identical emission spectra for each sample associated with the Pr3+ ions. Among them, the S3 sample exhibited the best ML properties and reproducibility due to the appropriate ratio of deep and shallow traps and luminescence centers, as suggested by the thermoluminescence spectra. A part of ML emission from LiTaO3:Pr also lies in an infrared biological window, which is another unique feature explored in this study. The outcomes validate LiTaO3:Pr as a promising candidate for the fast, sensitive, and remote detection of diverse mechanical stimuli in various industrial and biological applications.