Multifunctional SrAl ₂ O ₄ :Eu ²⁺ ,Dy ³⁺ – Borotellurite Glass Composite for Persistent Luminescence and Eu ²⁺ /Sm ³⁺ -Based Optical Thermometry

The optical performance of persistent phosphors like SrAl2O4:Eu2+,Dy3+ is limited due to environmental sensitivity. We fabricated a multifunctional phosphor–glass composite in which crystalline SrAl2O4:Eu2+,Dy3+ particles are embedded within a Sm3+-activated borotellurite glass matrix, enabling simultaneous stabilization of defect-mediated persistent luminescence and self-referenced optical thermometry. Structural and microscopic analyses confirm retention of phosphor crystallinity and homogeneous dispersion within the host. The composite exhibits dual-channel emission composed of broadband Eu2+ (5d–4f) and sharp Sm3+ (4f–4f) transitions, allowing luminescence intensity ratio (LIR) thermometry over 293–523 K from a distance of ∼30 feet. The material exhibits a maximum absolute sensitivity of 4.9 × 10–3 K–1 and relative sensitivity up to 1.31% K–1 for 520/646 nm emission intensity ratio, demonstrating multichannel sensing capability. Electron paramagnetic resonance (EPR) and thermoluminescence (TL) analyses reveal partial passivation of oxygen-vacancy related traps and redistribution of trap depths in the composite. Time-resolved emission spectroscopy shows a reduction in Eu2+ lifetime from 4.5 to 1.1 ns, indicating increased transition probability caused by interfacial crystal-field modification. These results establish phosphor-glass composites as a versatile platform for integrating persistent luminescence, defect engineering, and high-precision ratiometric thermometry within a single robust material system.