Yb³⁺/Tb³⁺/Ho³⁺: phosphate nanophase embedded glass ceramics: enhanced upconversion emission and temperature sensing behavior

Yb³⁺/Tb³⁺/Ho³⁺ tri-doped transparent phosphate glass–ceramics (GCs) were successfully synthetized by a conventional melt-quenching technique with subsequent glass crystallization. The formation of phosphate nanocrystals (NCs) with leucite structure was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected-area electron diffraction (SAED). The variation of the decay curves confirms the accumulation of active centers into the NCs lattice. Hence, the UC emission intensity of Yb³⁺/Tb³⁺/Ho³⁺ doped GC610 sample is greatly enhanced relative to that in precursor glass (PG). And the UC energy transfers processes were systematically analysis. The result shows that the energy transfer of Ho³⁺→Tb³⁺ exists while Yb³⁺ as a sensitizer ion. Furthermore, the temperature-dependent UC luminescence and temperature sensing behaviors of the prepared materials based on the thermally coupled levels of Tb^{3+: 5}D₄ and Ho^{3+: 5}F₅ in the temperature range of 298–648 K were systematically investigated, to explore its possible application as optical thermometric medium, by utilizing the fluorescence intensity ratio (FIR) technique. The relative sensitivity (Sr) of 7.5 × 10⁻³ K⁻¹ and absolute sensitivity (Sa) of 22 × 10⁻³ K⁻¹ are achieved in the Yb³⁺/Tb³⁺/Ho³⁺ tri-doped GC. This GC materials is a very promising candidate for optical temperature sensors.