Photoluminescence and thermoluminescence properties of Er3+ doped MgGa2O4 nanoparticles: a dual-mode visible-NIR phosphor for optoelectronic and dosimetric applications

Abstract

Er³⁺-doped MgGa₂O₄ nanoparticles with varying concentrations (0–9 mol%) were synthesized using the self-combustion method and systematically analyzed for structural, optical, and dosimetry performance. XRD confirmed a single-phase cubic spinel structure (JCPDS 10-0113), while SEM, EDX, and HRTEM revealed uniformly distributed nanocrystals (∼51 nm) with homogeneous composition. UV-vis diffuse reflectance spectra showed a band gap decrease from 5.17 to 4.86 eV with increasing Er³⁺, attributed to defect-induced band tailing. FTIR confirmed characteristic Mg–O and Ga–O vibrations, validating structural integrity. Photoluminescence studies exhibited intense green (⁴S_3/2 → ⁴I_15/2) and NIR (⁴I_13/2 → ⁴I_15/2) emissions, with maximum intensity, extended lifetime (3.2 ns), and high quantum yield (58.29%) at 3 mol% Er³⁺. CIE and CCT analyses placed the emission in the green-yellow region having CCT ∼5291 K, suitable for WLEDs. Thermoluminescence (TL) glow curves displayed a single prominent peak at ∼200 °C, with highest intensity for 5 mol% Er³⁺ at 5 kGy dose, corresponding to medium-depth traps (E = 0.9–1.0 eV). Deconvolution revealed two trap types: shallow (oxygen vacancies) and deep (Er³⁺–V₀/Er³⁺–Ga⁺ complexes). The synergistic optical and TL performance confirms MgGa₂O₄:Er³⁺ as a promising multifunctional phosphor for WLED and γ-ray dosimetry applications.