The Evolution and Role of NH_4Cl Flux Used to Synthesize Sr_2SiO_4:Dy~(3+) Phosphor by Solid-State Reaction Method

摘要

Two different Sr_2SiO_4:Dy~(3+) phosphors were successfully synthesized at 1000℃ for 4 h using NH_4C1 or SrCl_2 as the flux, respectively. The luminescence intensity of Sr_2SiO_4:Dy~(3+) was enhanced 60 times by the addition of 5 wt% NH_4C1. The phase evolution and photoluminescence (PL) properties of the phosphors were investigated by the calculation of phase equilibrium and the analysis of TG/DSC, XRD, SEM, and PL. The role of NH_4C1 was proved to be attributed to the formation of SrCl_2 at ～300℃. The flux NH_4C1 or SrCl_2 lowered the decomposition temperature of carbonate and promoted the preferential formation of a' phase in the solid-state reaction through accelerating the kinetics of the formation of Sr_2SiO_4 by enhancing diffusion with more liquid phase.