Trap-controlled mechanoluminescence in Pr3+-activated M2Nb2O7 (M = Sr, Ca) isomorphic perovskites

Isomorphic materials tend to exhibit differentiated performance due to the small differences between the constituent atoms and the crystal structures. Inspired by the isomorphic strategy, herein we developed a novel trap-controlled mechanoluminescent (TC-ML) material, Pr3+-activated Sr2Nb2O7, that shows mechanoluminescence (ML) under the mechanical actions of compression and friction. Compared to the isomorphic Ca2Nb2O7:Pr3+ which requires a long-time delay to achieve high-contrast ML due to the strong long-lasting afterglow, Sr2Nb2O7:Pr3+ enables the obtaining of high-contrast ML in a short-time delay because of the weak short-lasting afterglow, which greatly simplifies the imaging process to facilitate the further application of ML. The investigations of structural and optical characteristics between Sr2Nb2O7:Pr3+ and Ca2Nb2O7:Pr3+ reveal that the unique ML of Sr2Nb2O7:Pr3+ should result from its lower trap concentration and shallower trap depth relative to Ca2Nb2O7:Pr3+. Our results are expected to deepen our understanding on the behavioral diversity of isomorphic phosphors and thereby broaden the horizon of designing and regulating TC-ML materials.