The effect of Yb ³⁺ co‐doping on relaxation dynamics of excited states of Er ³⁺ ion in oxyfluoro tellurite (TZYN) glasses was demonstrated employing excitation and luminescence spectroscopy. The up‐conversion luminescence spectra were studied as a function of temperature in the 298–633 K range, and fluorescence intensity ratio (FIR) for green bands due to the ² H _11/2 → ⁴ I _15/2 and ⁴ S _3/2 → ⁴ I _15/2 transitions of Er ³⁺ ion against temperature was determined. The temperature sensing performance of TZYN:Er ³⁺ /Yb ³⁺ glasses was studied using the FIR technique up to 633 K. The maximum absolute ( S _a ) and relative ( S _r ) sensitivity of 0.00246 K ⁻¹ at 413 K and 0.72% K ⁻¹ at 323 K, respectively, were determined for TZYN:0.5Er ³⁺ /1.0 Yb ³⁺ glass.

Dysprosium‐doped borophosphate glasses, containing the divalent cations Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ , are prepared by the melt‐quenching technique. The structure of the glasses is investigated by Raman, infrared, and nuclear magnetic resonance (NMR) spectroscopies and the fluorescence properties are determined. The Dy ³⁺ emission lifetime increases with an increasing ionic field strength and its maximum is observed in the Mg ²⁺ and Zn ²⁺ containing glasses. This result can be explained by the stronger M‐O bonding which causes a rearrangement of the borophosphate network and creates a local Dy ³⁺ environment of comparably low symmetry. This is in agreement with the Raman spectra and the evolution of the molar volume. The effect of the B/P variation on the emission properties of Dy ³⁺ is investigated in a second series of glasses where the emission lifetime is found to be maximum at 10 mol% B ₂ O ₃ .