Dual-phase glass ceramics for dual-modal optical thermometry through a spatial isolation strategy

Glass ceramics (GCs) can be an ideal medium for dopant spatial isolation, avoiding the adverse energy transfer process. Herein, a spatial isolation strategy is proposed and fulfilled by dual-phase GCs. Structural characterization performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), verified the successful dual-phase precipitation of tetragonal LiYF4 and cubic ZnAl2O4 nanocrystals (NCs) among aluminosilicate glasses. Impressively, it is evidenced that intense blue upconversion (UC) emission of Tm3+ and deep red DS emission can be attained simultaneously upon 980 nm NIR and 400 nm violet light excitation, respectively, owing to the extremely suppressed adverse energy transfer process between physically separated Tm3+ and Cr3+. This also suggests the partition of Yb3+ and Tm3+ into LiYF4 and Cr3+ into ZnAl2O4 respectively. In particular, optical thermometry based on the fluorescence intensity ratio (FIR) of Tm3+ and fluorescence lifetime of Cr3+ of dual-phase GCs were also performed in detail, with the maximum relative sensitivity of 1.87% K-1 at 396 K and 0.81% K-1 at 503 K, respectively. As a consequence, such a spatial isolation strategy would provide a convenient route for application in optical thermometry and extend the practical application of GC materials.