Chemical tuning of photo- and persistent luminescence of Cr3+-activated -Ga2O3 by alloying with Al2O3 and In2O3

An effect of alloying of the monoclinic beta-Ga2O3 with Al2O3 and In2O3 on the photoluminescent, thermoluminescent and persistent luminescent properties of Cr3+ ions has been comprehensively investigated. For this purpose, various series of Cr3+ and Ca2+ co-doped microcrystalline phosphors were synthesized by the solution combustion method, including pseudobinary compounds like (Ga-Al)2O3 with up to 20 % Al and (Ga-In)2O3 with up to 50 % In as well as pseudoternary compounds (Ga-Al-In)2O3 with balanced proportion of Al, Ga and In. The phase composition and crystal structure of the obtained materials were examined by X-ray powder diffraction technique. Detailed luminescence studies were conducted for the (Ga-Al)2O3 and (Ga-In)2O3 compounds which exhibited a single-phase monoclinic structure. Low-temperature and time-resolved photoluminescence investigations of the Cr-doped pseudobinary compounds unveiled several types of Cr3+ centres, attributed to the Al-, Ga- and In-centred octahedra in the studied alloys. The obtained results underscore the benefit of bandgap engineering through alteration in the host lattice chemical composition for efficient tuning of the thermoluminescent and persistent luminescent properties of the near-infrared-emitting beta-Ga2O3:Cr based phosphors. Furthermore, it was demonstrated that modification of the chemical composition of the host lattice also adjusts the thermometric performance of the studied phosphors. Indeed, the specific sensitivity of the beta-Ga2O3:Cr3+ decay time luminescence thermometer showed nearly twofold enhancement when the host lattice was alloyed with 30 % of In2O3.