Combustion synthesis and characterization of MV_0.5P_0.5O₄: Sm³⁺ Tm³⁺ (M = Gd, La, Y)

In this paper, GdV_0.5P_0.5O₄: Sm³⁺, Tm³⁺, LaV_0.5P_0.5O₄: Sm³⁺, Tm³⁺ and YV_0.5P_0.5O₄: Sm³⁺, Tm³⁺ phosphor powders were prepared by solution combustion method using urea as a fuel. The phase purity, surface morphology, optical and photoluminescence properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis spectroscopy and photoluminescence spectroscopy. The XRD results indicated that the prepared powders are of a single phase and crystallized in tetragonal structure for Gd and Y systems while monoclinic phase was observed for La system. SEM showed that the samples consisted of mixed structures. The estimated band gaps were 2.2, 2.4 and 2.3 eV for Y, Gd and La systems respectively. The photoluminescence results showed four emission peaks. One peak is assigned to ¹G₄ — ³H₆ transition of Tm³⁺, and three other emission peaks are attributed to ⁶G_5/2 — ⁶H_5/2, ⁶G_5/2 — ⁶H_7/2 and ⁶G_5/2 — ⁶H_9/2 transitions of Sm³⁺. The photoluminescent intensity was the highest in the gadolinium system.