1：Experimental Design and Method Selection:

The study employed traditional melt-quenching technique and subsequent heat treatment to fabricate Er3+/Yb3+ co-doped phosphate glass ceramics. Structural characterization was performed using XRD and TEM. Optical properties were investigated through absorption spectra, photoluminescence spectra, pump power dependent UC emission spectra, and UC decay curves. Temperature-dependent UC emission spectra were measured for optical thermometry based on FIR technique.

2：Sample Selection and Data Sources:

Samples were prepared with chemical compositions (in mol%): 20K2O–40ZnO–30P2O5–10B2O3–1Yb2O3–xEr2O3 (x = 0.025, 0.05, 0.075 and 0.1). Raw materials included K2CO3, ZnO, NH4H2PO4, H3BO3, Yb2O3 and Er2O

3：025, 05, 075 and 1). Raw materials included K2CO3, ZnO, NH4H2PO4, H3BO3, Yb2O3 and Er2OList of Experimental Equipment and Materials:

3. 3. List of Experimental Equipment and Materials: X-ray powder diffractometer (D8-Advance, BRUKER), transmission electron microscopy (TEM, Tecnai G2 F20 S-TWIN, FEI), fluorescence spectrometer (FuoroSENS9000A), 980 nm laser diode (MDL-III-16110236), Edinburgh Instruments FS5 spectrofluorometer, temperature controlling stage (HFS600E-PB2, Linkam).

4：Experimental Procedures and Operational Workflow:

Raw materials were mixed, calcined at 600°C for 60 min, melted at 1250°C for 100 min, quenched into a copper mold, annealed at 400°C for 10 h to form precursor glass (PG). PG pieces were heat-treated at 610°C for 6 h to form glass ceramics (GC). Samples were polished for characterization. UC emission spectra were recorded under 980 nm laser excitation, and temperature-dependent measurements were conducted from 298 to 798 K.

5：Data Analysis Methods:

XRD patterns analyzed for crystallinity, TEM for microstructure, UC emission intensities analyzed using power law, FIR calculated from emission intensities, sensitivity parameters derived from Boltzmann distribution equations.