Understanding the Influence of Electron Traps and Urbach States on the Kinetics of Ti3+ Persistent Luminescence in LaAlO3:Ti3+

Abstract

The luminescence kinetics of Ti3+ ions, resulting from the spin-allowed 2E → 2T2 electron transition, are generally expected to be fast, within the microsecond range. However, in this study, we observed average lifetimes of up to 30 ms in nanocrystalline LaAlO3:Ti3+ powders. Our detailed analysis of the spectroscopic and thermoluminescence properties of LaAlO3:Ti3+ suggests that this prolonged Ti3+ kinetics is associated with the presence of electron traps and the proximity of the Ti3+ excited state to the conduction band, which facilitates energy transfer between them. Furthermore, the observed shift in Urbach states with an increasing Ti3+ concentration correlates with the efficiency of energy transfer between deeper traps and Ti3+ ions. This study provides a comprehensive strategy for controlling the luminescence kinetics of Ti3+ ions through electron trap engineering, induced by dopant ion concentration, which can be applied in various fields including luminescence thermometry.