Citrate-based sol-gel synthesis of blue- and green-emitting BaLa₂WO₇:Tm³⁺ or Er³⁺ phosphors and their luminescence properties

Highlights: • The BLWO:Tm³⁺ or Er³⁺ phosphors were prepared by a citrate-based sol-gel method. • The BLWO:Tm³⁺ or Er³⁺ phosphors exhibited blue and green emissions under UV or NUV excitations. • The blue- and green-emitting BLWO:Tm³⁺ or Er³⁺ phosphors exhibited good thermal properties. - Abstract: BaLa₂WO₇:Tm³⁺ or Er³⁺ (BLWO:Tm³⁺ or Er³⁺) single doped phosphors were prepared by a citrate-based sol-gel method. The crystalline properties of the prepared blue- and green-emitting phosphor materials were analyzed by X-ray diffraction (XRD) after annealing at 1350 °C. The XRD patterns of the both phosphors revealed monoclinic structure with a space group of P21/b. The morphological properties and elemental mappings of the BLWO:0.02Tm³⁺ and BLWO:0.01Er³⁺ phosphors were measured by field-emission scanning electron microscope images and energy dispersive X-ray spectrum, respectively. The photoluminescence (PL) spectra of BLWO:Tm³⁺ phosphors showed characteristic emission peaks of Tm³⁺ ions from the visible blue to near-infrared regions with the dominant emission at 799 nm (³H₄ → ³H₆) under ultraviolet (UV) and near-UV excitation wavelengths. Similarly, Er³⁺ ions activated BLWO phosphors exhibited intense green emissions at 548 nm (⁴S_3/2 → ⁴I_15/2) under the characteristic excitation wavelength of 381 nm. Furthermore, the temperature-dependent PL emission spectra and the luminescence decay curves were measured for the optimized BLWO:0.02Tm³⁺ and BLWO:0.01Er³⁺ phosphors. The chromaticity coordinates for the optimized blue- and green-emitting phosphors were calculated.