Tuning the crystal structure, optical band gap and persistent luminescence performance of Cr 3+ -doped LiGa 5 O 8 spinel by adding aluminum and indium

Abstract

The possibility of tuning the optical band gap, crystal structure and persistent luminescence performance of Cr 3+ -doped LiGa 5 O 8 spinel by partially replacing Ga with Al and/or In has been studied extensively. For this purpose, a series of Cr 3+ -doped Li(Ga 1-x-y Al x In y ) 5 O 8 (x = 0…0.5; y = 0…0.1) microcrystalline phosphors were synthesized using a conventional solid-state reaction method and characterized by powder X-ray diffraction and luminescence techniques.The DFT-based electronic structure calculations were carried out for the same Li(Ga 1-x-y Al x In y ) 5 O 8 compositions, and the results were compared with the experimental ones.Based on the studies performed, the mechanism of Al and In incorporation into the LiGa 5 O 8 spinel structure, as well as the tuning of the crystal lattice parameters, local structure of M 3+ (M = Ga, Al, In) cations and optical band gap of the material have been established. The multicenter structure and the broadening of the local structural disorder of the octahedrally coordinated Cr 3+ centers observed in this case have been confirmed by the high-resolution, lowtemperature photoluminescence measurements. Band gap engineering through alterations in the chemical composition of the LiGa 5 O 8 spinel, as well as the depth of the native point defects responsible for charge trapping, allows for the efficient tuning of the thermoluminescent and persistent luminescent properties of Li(Ga 1-x-y Al x In y ) 5 O 8 :Cr 3+ phosphors. Thus, the roomtemperature persistent luminescence performance of the phosphors modified by the addition of Al and annealing in an oxygen-free atmosphere was increased threefold compared to the pristine LiGa 5 O 8 :Cr 3+ phosphor synthesized under the same conditions.