Spectroscopic investigation of La7Ta3W4O30:Sm3+ orange-red phosphor for white LEDs

The novel orange-red light emitting La7Ta3W4O30:xSm3+ (x = 0.005–0.20) phosphors were synthesized via the solid-state reaction method. The crystal structure, photoluminescence (PL) properties, optimum concentration, color purity, decay life, and thermal stability of the samples were systematically studied. Under the excitation of 404 nm, La7Ta3W4O30:Sm3+ emits intense orange-red light at 597 nm. The PL spectra of La7Ta3W4O30:Sm3+ phosphors are ascribed to the 4G5/2 to 6HJ (J = 5/2, 7/2, 9/2, and 11/2) transitions of Sm3+ ions. The concentration quenching occurs at the doping level of 1 mol%. The quenching temperature is higher than 500 K. Finally, a white LED (w-LED) with the Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of (0.312, 0.296) and good color rendering index (Ra) of 86 was fabricated. As a consequence, all the results suggest that the orange-red phosphors La7Ta3W4O30:Sm3+ have potential applications in w-LEDs structures.