The evolution and role of NH4C1 flux used to synthesize double perovskite BaLaMgSbO_6: a potential red phosphor for white LEDs

摘要

Abstract Eu3+ ions activated BaLaMgSbO_6 phosphors were successfully synthesized by the solid-state reaction method using NH_4C1 as the flux. The BaCl_2 was selected to substitute BaCO_3 as the starting material to attest that NH_4C1 not only reacted with BaCO_3 but also reacted with other starting materials. The analysis of TG/DSC was used to probe the role of NH_4C_1 flux in the process of synthesizing BaLaMgSbO_6 powders. The crystal structure was investigated by XRD and Rietveld refinement, and the morphology by SEM. The phosphors had monoclinic double perovskite structure with the space group P21, as well as the rock-salt ordering of B-site. The luminescence properties, including the photoluminescence excitation and emission spectra, and the color coordinates were investigated. Also, the relationship between the crystalline size and the emission intensity were discussed. With increasing the calcination temperature, both the crystalline size and the emission intensity monotonously increased. The relative intensity ratio of red/orange emission was used to measure the degree of distortion from the inversion symmetry of the local environment of the Eu~(3+) ions in BaLaMgSbO_6.