Interstitial oxygen defect induced mechanoluminescence in KCa(PO3)3:Mn2+

Abstract

Elastic mechanoluminescent materials, which are easily affected by inner defects, have attracted extensive attention due to their excellent performance in various detection and display fields. However, definitive experimental and theoretical evidence of the defect types in these materials is scarce. In this study, a series of KCa(PO₃)₃:Mn²⁺ mechanoluminescent materials are studied using X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, thermoluminescence, and first-principles calculations. The defect types and the mechanisms of the mechanoluminescent materials are clarified. The interstitial oxygen atoms formed during the self-reduction of Mn⁴⁺ to Mn²⁺ are crucial for forming the trap levels and inducing mechanoluminescence. Cation substitution of Mg²⁺ for Ca²⁺ in the flexible structure of KCa(PO₃)₃ promotes the luminescence properties by minimizing the Helmholtz free energy and deepening the position of the defect level. This study highlights the importance of defects in the material properties and provides new insight for selecting research systems to develop novel optical functional materials.