Phase formations and tunable red luminescence of Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0)

Abstract

Mn2+-doped phosphates Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) were prepared by conventional solid-state reaction. X-ray powder diffraction (XRD), the emission and excitation spectra, and decay measurements were employed to characterize the synthesized phosphors. The XRD patterns show that Na2CaMg1−xMnx(PO4)2 (x = 0.05–0.3) forms the single low temperature monoclinic phase α-Na2CaMg(PO4)2 with the crystal group of P21/c (No.14). The heavily Mn2+-doped Na2CaMg1−xMnx(PO4)2 (x = 0.6–1.0) crystallizes in the single high-temperature trigonal phase of β-Na2CaMg(PO4)2 with space-groupPm1 (No. 164). The members with x = 0.3–0.5 form a series of solid solutions containing two distinct phases, α- and β-Na2CaMg(PO4)2. The dependence of luminescence spectra on the Mn2+-doping concentration in Na2CaMg1−xMnx(PO4)2 (x = 0.05–1.0) was investigated. The great red-shift of Mn2+ emission with increasing Mn2+-concentration in Na2CaMg(PO4)2 were observed. The results are discussed in relation with the detailed crystal structure and the spectral analyses. The CIE coordinates and the luminescence decay (lifetimes) of Mn2+ ions were discussed in order to further investigate the potential applications.