Study of the up/down-conversion green luminescence of BaWO4: Er3+ phosphors for non-contact temperature sensing and solid-state lighting applications

The reported article covers the down-conversion (DC) and up-conversion (UC) photoluminescence properties of BaWO4 (BWO): Er3+ phosphors, prepared via solid-state reaction route. The prepared samples were subjected to various characterization tools and spectroscopic techniques such as XRD, FESEM, EDX, XPS, PL, FTIR and UV–Vis-NIR for structural and optical characterizations. Intense green emission was achieved from both down-conversion and up-conversion emission spectra under UV excitation of 378 nm and near-infrared excitation of 980 nm, respectively. Green LED is fabricated using a 365 nm UV chip to ensure the performance of the material. The luminescence quenching was observed above 0.5 mol% doping of Er3+, governed by dipole–quadrupole interaction. Decay curves of all samples follow single exponential behavior and the average decay time reduces with the increase of Er3+ concentration. Temperature-dependent UC emission spectra were recorded within 300–500 K. The emission intensity was maintained at 82% at 147 °C compared to the intensity at room temperature, suggesting the good thermal stability of the BWO: Er3+ phosphors. The change in the fluorescence intensity ratio (FIR) between two thermally coupled energy levels of Er3+ ion with temperature has been utilized to investigate the temperature-sensing properties of the reported phosphors. The maximum relative temperature sensitivity was found to be 9.97 × 10–3 K−1 at 300 K. Obtained efficient green emission and comparatively good sensitivity make the proposed phosphor material a promising candidate for the color mixing component of phosphor-converted WLED and temperature-sensing applications.