Structure, luminescence and temperature sensing in rare earth doped glass ceramics containing NaY(WO₄)₂ nanocrystals

Novel rare earth doped glass ceramics containing NaY(WO₄)₂ nanocrystals were fabricated for the first time. The appearance of sharp diffraction peaks and well-resolved lattice fringes certifies the precipitation of NaY(WO₄)₂ nanocrystals with high crystallinity. After the crystallization process, significant changes in the photoluminescence emission spectra and fluorescence lifetime of Sm³⁺ ions are observed, which are ascribable to the enrichment of Sm³⁺ ions in the highly disordered NaY(WO₄)₂ nanocrystals. Under 980 nm excitation, characteristic green and red upconversion emission signals were detected and the enhanced upconversion luminescence of Er³⁺ ions in the glass ceramics was attributable to the incorporation into the low energy phonon NaY(WO₄)₂ nanocrystals. Based on the dependence of upconversion intensity on the excitation power, the upconversion mechanism of Er³⁺-Yb³⁺ ions was proposed. The temperature-dependent fluorescence intensity ratio (FIR) of the thermally-coupled ²H_11/2 and ⁴S_3/2 energy levels was determined at a low power density of 0.4125 W cm^-2. The maximum temperature sensitivity is 146 × 10^-4 K^-1 at 523 K, which is mainly attributed to the highly disordered structure of NaY(WO₄)₂ nanocrystals and exhibits promising potential for optical temperature sensors.