Impact of annealing time on self-activated red-emitting La2ZnTiO6 nanophosphors synthesized by the sol–gel method for white LED applications

The development of efficient phosphors with favourable optoelectronic properties is essential for improving white lighting diodes (wLEDs) and other optoelectronic applications. In this study, self-activated red-emitting La 2 ZnTiO 6 (LZTO) nanophosphors were synthesised via the sol-gel method, and the influence of annealing time on their thermal, structural, morphological, and optical properties were systematically investigated. Thermogravimetric analysis confirmed thermal stability at 1000 ℃. X-ray powder diffraction results confirmed the formation of single-phase monoclinic LZTO with the P 21/ n space group and enhanced crystallinity after annealing. X-ray photoelectron spectroscopy confirmed the presence of La, Zn, Ti, and O, indicating high chemical purity, while Field-emission scanning electron microscopy revealed progressive morphological evolution with annealing. UV–visible diffuse reflectance spectra exhibited two absorption band edges located at 300–333 nm and 376–390 nm, with the indirect optical bandgap ranging from 3.14 to 3.20 eV. Under 3.17 eV excitation, LZTO exhibited reddish-orange emission with prominent red bands at 1.82, 1.75, and 1.68 eV, which were primarily associated with oxygen-vacancy-related defects and surface states. The emission intensity increased with annealing time and reached an optimum after 6 h. Temperature-dependent PL measurement revealed gradual thermal quenching from 303 to 423 K. At 423 K, only 5.65% of the initial emission intensity was retained, indicating limited thermal stability. Nevertheless, the Commission Internationale de l’Éclairage chromaticity coordinates showed negligible temperature variation, demonstrating good colour stability. These findings highlight the potential of annealed LZTO nanophosphors as self-activated red-emitting materials for high-quality solid-state lighting and related optoelectronic technologies and systems.