Evaluation of luminescent and thermal properties of Dy³⁺ doped tungstate phosphors for optoelectronic and thermometry applications

Novel Ca₂MgWO₆: xDy³⁺ (x = 1, 2, 3, 4, and 6 mol%) phosphors were synthesized via solid-state reaction method. The phosphor structure remained unchanged upon doping with Dy³⁺ ions. Phosphors were optical optimizated using ⁴F_9/2 → ⁶H_13/2 transition, and 3 mol% of Dy³⁺ was found to be optimal concentration. We investigated optical quenching mechanisms including energy transfer, cross-relaxation, charge compensation, and multipole-multipole interactions. Colorimetric analyses assessed colour coordinates, purity, and correlated colour temperature (CCT). The optimized phosphor showed a direct band gap of 3.68 eV, a refractive index of 2.24, and covalent bonding between Dy³⁺ and the host. It exhibited exceptional thermal stability with only 0.31 wt% loss up to 440 °C. Temperature-dependent emission spectra indicated high optical quenching temperature (498.82 K) and activation energy (0.21 eV). A multi-transition ratiometric approach confirmed suitability for non-contact thermometry and LED applications.