Exploring thermal enhancing of luminescence in Y2(WO4)3·3H2O:xmol%Eu3+ phosphors

A series of Y₂(WO₄)₃·3H₂O:xmol%Eu³⁺ (YWO:xEu) red phosphors were prepared. The structure, morphology, composition, photoluminescent (PL) characteristics, and thermal stability were systematically investigated. The samples underwent a structural phase transformation from the orthorhombic to the monoclinic phase with increasing x from 0 to 70 mol%. Due to the transformation in the crystalline phase of the phosphors, the bandgap energy (E_g), the PL intensity, and the fluorescence decay lifetime exhibited significant change. The YWO:5Eu and YWO:20Eu phosphors exhibited thermal enhancing of luminescence (TEL) at 175 °C. Under the monitoring of ⁵D₀→⁷F₂ transition, the maximum excitation intensities reached 7.28 and 4.46 times of those at room temperature. With CTB excitation, the maximum emission intensities were 7.13 and 5.10 times of the corresponding initial emission intensities. In contrast, YWO:50Eu displayed thermal quenching of luminescence (TQL). Combined with in situ X-ray diffraction (XRD) patterns, Rietveld refinement results, thermogravimetric (TG) analyses, and X-ray photoelectron spectroscopy (XPS) data, the mechanism of TEL can be explained by the release of H₂O molecules and the negative thermal expansion (NTE) of Y₂(WO₄)₃. This study provides guidance for exploring efficient red phosphors with thermal stability.