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

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.