Impact of heat treatment on structural and optical properties of europium based phosphate glasses for photonic applications

Effect of heat treatment on optical and structural properties of Eu³⁺-doped glasses with composition xEu₂O₃-20BaO-20Bi₂O₃-1.5Al₂O₃-(58.5-x)P₂O₅ (x = 0, 0.5, 1.0, 1.5 mol%) are investigated. XRD pattern reveals the commencement of crystallization, attributed to the segregation of crystalline phases of barium, bismuth and phosphate. EDX analysis confirms the presence of Ba, Bi. P, O, Eu and Al in all samples, except HT-0.0-EuBiPBa sample which shows no detectable Eu-content. Increasing content of Eu₂O₃ promotes crystallization. Optical studies demonstrated that absorption band is slightly blue shifted (from 457 nm to 450 nm). A decrease in optical bandgap across all samples is linked to introduction of defect states on heating. Photoluminescence measurements showed enhanced luminescence intensity, particularly in the hypersensitive ⁵D₀ → ⁷F₂ transition, indicating improved local environment around Eu³⁺ ions. Concentration quenching is evident on increasing the content of Eu₂O₃ beyond 1.0 mol%. Findings highlight the potential of heat treatment to tailor the properties of rare-earth doped glasses for photonics applications.