Exploring the viability of thermally robust β-BaB₂O₄: Dy³⁺ through FIR based polynomial approach for advanced temperature sensing and WLED applications

In this present work, we have explored the optical, structural, and thermal sensing properties of novel β-BaB₂O₄: xDy³⁺ (x = 1, 2, 3, 4, and 5 mol%) phosphors prepared using the solid-state reaction method. The optimization of the phosphors was achieved by using the characteristic emission spectra of Dy³⁺ ions. A thorough investigation was conducted into the various mechanisms contributing to concentration quenching, including cross-relaxation pathways, multipole-multipole interactions, and non-radiative energy transfer processes. Using the diffused reflectance spectra, significant parameters including optical band gap, nephelauxetic ratio, bonding parameter, and refractive index were evaluated. Temperature-dependent optical properties revealed a very high quenching temperature of 492.7 K. Using the florescent intensity ratio (FIR) with polynomial fit from 2nd to 5th order, the highest absolute sensitivity was obtained as 0.0472 K⁻¹ at 483 K, and the highest relative sensitivity of 0.3922 % K⁻¹ at 303. Finally, the optimized phosphor exhibited exceptional thermal stability up to 500˚C with nearly 1 wt% of loss.