Synthesis and Properties of Sm³⁺/Gd³⁺ Co-Doped B₂O₃–GeO₂–Bi₂O₃ Glass Composition

Within the scope of the study, glasses co-doped with Sm³⁺/Gd³⁺ based on the B₂O₃–GeO₂–Bi₂O₃ system were synthesized, covering compositions of 40B₂O₃–40GeO₂–(15 – 17)Bi₂O₃–(3 – 2)Sm₂O₃–(2 – 1)Gd₂O₃ and 42.5B₂O₃–42.5GeO₂–(11.25 – 12.75)Bi₂O₃–(2.25 – 1.50)Sm₂O₃–(1.500 – 0.075)Gd₂O₃. An assessment of luminescent characteristics was carried out within the temperature range of 298 – 673 K. Spectral bands of photoluminescence associated with transitions between various Stark sublevels of Sm³⁺ ions were identified. Redistribution of the fluorescence intensity ratio corresponding to ⁴G_5/2 → ⁶H_9/2 ( \({\uplambda }_{\mathrm{PL}}^{\mathrm{max}}\) ${\mathrm{\lambda }}_{\mathrm{PL}}^{\max }$ = 645 nm) and ⁴G_5/2 → ⁶H_7/2 ( \({\uplambda }_{\mathrm{PL}}^{\mathrm{max}}\) ${\mathrm{\lambda }}_{\mathrm{PL}}^{\max }$ = 597 nm) transitions was observed. Based on the obtained data, calculations of the fluorescence intensity ratio FIR, as well as relative sensitivity S_R, were carried out. The obtained results indicate the promising potential of these glasses as luminescent thermometric materials.