This distinctive thermal response could be applied in temperature sensing, as demonstrated by a high relative sensitivity (Sr) of 1.22% K-1 at room temperature (303 K), which is superior to many reported optical thermometry materials. Interestingly, Mn2+ green emissions presented excellent anti-thermal quenching (165.4% at 463 K) in a very wide temperature range (303─463 K), whereas severe thermal quenching was observed for the Mn4+ red emissions. ![]() ![]() This self-reduction can be effectively inhibited by the site-selective Al3+-to-Ga3+ substitution in MGySO:Mn2+/4+, thereby resulting in an accumulation of Mn ions in the octahedrally coordinated sites and tunable emission colour from green to yellow and then to deep-red. Mn-activated MGSO exhibited dual emissions from multiple green-emitting Mn2+ and red-emitting Mn4+ activators due to the facial occurrence of Mn4+-to-Mn2+ self-reduction, which is inevitable in Mn-doped spinel-type phosphors. A joint hybrid density functional theory (DFT) calculation and crystal orbital Hamilton population (COHP) analysis demonstrated that these new spinels are direct semiconductors with band gap values increase along with Al3+-content due to the lift of anti-bonding states from the Sb2−O pairs. Herein, spinel-type oxides Mg4Ga1-yAlySbO8 (MGAySO) with a double 2:1 ordering of Mg/(Ga/Al) and Mg/Sb cations in tetrahedral and octahedral sublattices, respectively, were rationally designed and structurally characterized by combined Rietveld refinements against high-resolution X-ray powder diffraction (XRPD) data and neutron powder diffraction (NPD) data. Mineral structure-stimulated material design has made great success in the development of excellent phosphor materials.
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