A Novel Zero-Thermal-Quenching Red Phosphor with High Quantum Efficiency and Color Purity

Abstract

In this paper, a series of K5La1-x(MoO4)4: xSm3+ and K5La0.86(MoO4)4: 0.07Sm3+, 0.07Ln3+ (Ln = Sc, Y or Gd) red phosphors were prepared by calcining the mixed raw powders at 600 °C. Meanwhile, the composition and fluorescence properties of the phosphors, especially for the thermal stability, were analyzed in detail. The results indicate that the K5La1-x(MoO4)4: xSm3+ phosphors can be effectively excited at 401 nm and emit red light with three main peaks at 561 nm, 600 nm and 646 nm, attributed to the 4G5/2→6Hj/2 (j = 5, 7 and 9) energy transitions of the Sm3+ ion respectively, among which the K5La0.93(MoO4)4: 0.07Sm3+ exhibits the highest intensity. The quenching mechanism is ascribed to the dipole-dipole interaction. Ln3+ co-doping does not change the shape and peaking position of the excitation and emission spectra of K5La0.93(MoO4)4: 0.07Sm3+, but further increases the emission intensity in different degrees. Particularly, K5La0.86(MoO4)4: 0.07Sm3+, 0.07Gd3+ demonstrates a high quantum efficiency of 74.63%, a low color temperature (1753 K), and a high color purity of up to 99.97%. It is worth noting that all the phosphors have a good thermal stability, even a zero quenching phenomenon occurs, attributed to the electron traps confirmed by the TL spectrum.