Vermillion light-emitting Gd2–xSmxO3 nanophosphors with 99% colour purity for warm light applications

Vermillion (reddish-orange) emitting Sm³⁺-doped Gd₂O₃ nanophosphors with colour purity of 99% have been successfully synthesized by using a facile low-temperature solution combustion method. The influence of Sm³⁺ concentration and annealing temperature on structural and optical properties has been studied in detail. The XRD studies confirm that the as-synthesised samples crystallize in multiphase, while a cubic phase is formed by annealing the samples at a temperature above 773 K. An FTIR study was carried out for compositional analysis. Diffuse reflectance profiles were used to measure the bandgap energies and the values were observed to be around 5 eV. Spherical-shaped morphology was confirmed by scanning electron microscopy image. Upon UV excitation of 260 nm, typical emission of Sm³⁺ ion associated with ⁴G_5/2 → ⁶H_J transitions (J = 5/2, 7/2, 9/2, 11/2) are seen, with the major emission peak being at 610 nm. The optimal doping concentration is 1 wt%. The lifetime value is about 0.75 ms. The CIE 1931 chromaticity diagram is used to specify the luminescence colour of the prepared samples. The colour coordinates range within the reddish-orange region, and the CCT value is less than 5000 K. These findings suggest that the incorporation of Sm³⁺ into Gd₂O₃ as a dopant holds promise for serving as reddish-orange emitting phosphor for warm white applications.