Dual-Phase Glass Ceramics Containing ZnGa₂O₄:Cr³⁺ and NaYF₄:Yb³⁺,Er³⁺ Nanocrystals for Dual-Mode Optical Thermometry

Currently, developing luminescent materials for dual-mode optical thermometry has been becoming a rising topic, and concurrent temperature-sensitive optical parameters hold the key. Still, it is a serious challenge, since distinct activators are generally needed and energy transfer (ET) processes among activators inevitably occur, further leading to severe luminescence quenching. Herein, a spatial separation strategy is proposed for designing dual-phase glass ceramics (GCs) containing ZnGa₂O₄:Cr³⁺ and NaYF₄:Yb³⁺,Er³⁺ nanocrystals (NCs) for dual-mode optical thermometry, in order to integrate diversified activators into one. Structural, morphological, and optical characterizations are examined to verify the partition of Cr³⁺ into ZnGa₂O₄ and Er³⁺ into the NaYF₄ lattice in the dual-phase GC. Benefiting from such a spatial separation strategy, the adverse ET processes between Cr³⁺ and Er³⁺ could be cut off in the dual-phase GC, contributing to downshifting (DS) and upconversion (UC) luminescence. Furthermore, dual-mode optical thermometry is performed based on the lifetime of Cr³⁺ and fluorescence intensity ratio (FIR) of Er³⁺, with high relative sensitivities of 0.95% K^-1@450 K and 1.24% K^-1@303 K, respectively. It is evidenced that the dual-phase GC holds great potential for dual-mode optical thermometry, and this work also offers a prospective pathway for expanding the practical applications of GC luminescent materials.