Construction of a novel mechanoluminescent phosphor Li₂MgGeO₄:xMn²⁺ by defect control

Abstract

Lattice defect plays a significant role for optical properties of elastic mechanoluminescent materials, which could be modulated by cationic non-equivalent replacement. Here a series of novel mechanoluminescent phosphors Li2-xMgGeO4:xMn2+ (0...

Intense Luminescence and Good Thermal Stability in a Mn2+-Activated Mg-Based Phosphor with Self-Reduction

“…After that, a portion of the electrons in CB relax non-radiatively to the lowest excited state of Mn 2+ (process ②). Finally, the orange-red light is produced through the electron transition from 4 T 1 to 6 A 1 of Mn 2+ . For ML, under the stimulation of mechanical forces, some of the trapped carriers in the trap energy levels are released to CB and then emit light through process ② (path ③).…”

Self-Reduction-Related Defects, Long Afterglow, and Mechanoluminescence in Centrosymmetric Li2ZnGeO4:Mn2+

“…It can be easily realized in the self-reduction system. Based on this concept, several new elastico-mechanoluminescent materials have been discovered one after another in our group. ,, But they all crystallize in non-centrosymmetric structures that people are accustomed to choosing. The centrosymmetric mechanoluminescent material Li 2 ZnGeO 4 : x Mn 2+ proves that our strategy of screening mechanoluminescent materials in a self-reduction system is more universally applicable.…”

Oxygen vacancy content drives self-reduction and anti-thermal quenching

“…According to previous studies, the self-reduction of transition and rare-earth metal ions in air are closely related to lattice defects, which would offer extra electrons to adjacent activators to turn them into a lower valence-state. [21][22][23][24]38 As shown in Fig. S5 (ESI †), the fitting coordinated number acquired by the extended X-ray absorption fine structure (EXAFS) spectra and Fourier transforms (FTs) decreases to 2.635 from 4, demonstrating the deficiency of the O-ligands around the center ion and further indicating the formation of oxygen vacancy defects (Vo) in the unit cell.…”

“…Enlightened by our previous studies, the valence state selfreduction of Mn ions (Mn 4+ -Mn 2+ ) in ambient atmosphere can be achieved and stabilized in specific hosts, such as the phosphates of AB(PO 3 ) 3 (A = Na, K; B = Ca, and Zn) and the germanates of C 2 MgGeO 4 (C = Li, Na). 8,[21][22][23][24] Benefitting from anionic groups [PO 4 ] 3À or [GeO 4 ] 4À , a rigid three-dimensional network framework is constructed to protect Mn 2+ ions from being oxidized at high temperatures, which lays the foundation of anti-TQ. However, it is far from sufficient to realize the process of self-reduction.…”