Revisiting Y3Al5−xGaxO12 Solid Solutions Doped with Chromium Ions: Effect of Local Symmetry on Thermal Quenching of Cr3+ and Cr4+ Ions

Abstract

The oxidation of chromium ions to the 4+ state in phosphors doped with Cr3+ ions is often considered negative due to the activation of the parasitic Cr3+→Cr4+ luminescence quenching channel. However, in this paper, a systematic study of the effect of host material stoichiometry on the spectroscopic properties of Cr4+ in Y3Al5−xGaxO12 is investigated to develop ratiometric luminescence thermometers. Correlations between the structural properties of the host and the luminescence thermal quenching process of Cr4+ ions emission associated with the 3B2→3B1 electronic transition enabled the development of a luminescence thermometer exploiting the ratio of Cr3+ to Cr4+ emissions with a relative sensitivity of 2.04%K−1. The studies carried out enabled a better understanding of the formation processes of Cr4+ ions.