Synthesis, substitutional sites and photoluminescence of Na2SrMg(PO4): Pr3+ phosphors

Pr3+-doped Na2SrMg(PO4)2 phosphors were successfully prepared by high temperature solid-state reaction. The phosphors were confirmed to be pure crystalline phase of Na2SrMg(PO4)2. The different substitutional sites and photoluminesent properties of the Pr3+ ions in Na2SrMg(PO4)2 were experimentally investigated in detail. The optimum doped concentrations of Pr3+ ions replace the host Na+, Sr2+, Mg2+ were determined and they are 1.0 mol%, 0.5 mol%, and 1.5 mol%, respectively. The phosphors could be excited by blue light and showed a reddish yellow emission with the strongest peak at 599 nm. The nine 4f levels corresponding to the f-f transitions of Pr3+ ions were identified. The average crystallite sizes and the critical distances of Pr3+ ions substitute Na+, Sr2+, Mg2+ sites are found to be about 46.4, 47.9, 45.2 nm, and 31.43, 39.60, 27.46 Å, respectively. The average CIE chromaticity coordinates of the Pr3+-doped Na2SrMg(PO4)2 phosphors upon 444 nm excitation are also proved that the emissions are located in the reddish yellow region. These results reveal that Na2SrMg(PO4)2:Pr3+ presents good photoluminescent properties and could be a potential candidate material for lighting application.