Mn 2+ -doped NaCaPO 4 were synthesized by a solid-state reaction. The structure and luminescence were investigated. The main excitation bands located at a band extending from 380 to 450 nm could match the emission of UV light emitting diode chips. The phosphors exhibited the emission in the wavelength range of 600-750 nm. The luminescence showed a redshift with the increase in Mn 2+ doping concentrations. This color points could be tunable by controlling the doping of Mn 2+ in NaCaPO 4 . The thermal stability of the luminescence of Mn 2+ ions was evaluated at different temperatures. The doping mechanism of Mn 2+ ions was discussed.The luminescence of Mn 2+ -ion-doped inorganic compounds usually gives a broad-band emission, which depends on the host lattice. From the Tanabe-Sugano diagram, the emission corresponds to the 4 T 1 → 6 A 1 transition in Mn 2+ ions and can vary in a wide range in all the spectral wavelengths. 1 For example, the tetrahedrally coordinated Mn 2+ usually gives a green emission, whereas the octahedrally coordinated Mn 2+ gives an orange to red emission. 2 This gives a wide usage of Mn 2+ -doped compounds for fluorescent lamps, cathode ray tubes, and potential applications in white light emitting diodes ͑LEDs͒. 3 In recent years, there has been an increased interest in the investigations of luminescent materials with the structures derived from the ABPO 4 family ͑A and B are mono-and divalent cations, respectively͒. For example, Eu 2+ -doped LiSrPO 4 was investigated to have a higher emission intensity compared with the blue-emitting phosphor BaMgAl 10 O 17 :Eu 2+ . 4 NaCaPO 4 :Eu 2+ was a potential greenemitting phosphor for white LEDs. 5 Eu 2+ -doped KSrPO 4 showed a higher thermally stable luminescence, which was better than commercially available Y 3 Al 5 O1 2 :Ce 3+ at a temperature higher than 225°C. 6 Chan et al. reported that Mn 2+ -doped LiZnPO 4 has potential applications as a green-yellow-emitting phosphor in LEDs. 7 In this work, NaCa 1−x Mn x PO 4 ͑x = 0.01, 0.05, 0.08, 0.12, 0.16, 0.20, 0.22͒ were prepared by solid-state reaction and were characterized by excitation and emission spectroscopes. The luminescence properties, e.g., the wavelength position, emission intensity, full wavelength at half-maximum ͑FWHM͒, and color coordinates, were discussed depending on the Mn 2+ doping levels. The thermal stability of the luminescence of Mn 2+ ions was evaluated at different temperatures. ExperimentalNaCa 1−x Mn x PO 4 ͑x = 0.01, 0.05, 0.08, 0.12, 0.16, 0.20, 0.22͒ phosphors were synthesized by solid-state reaction. The starting material was a stoichiometric mixture of reagent grade Na 2 CO 3 , CaCO 3 , NH 4 H 2 PO 4 , and MnCO 3 . First, the mixture was heated up to 350°C and kept at this temperature for 10 h. The obtained powder was thoroughly mixed and then heated up to 750°C and was kept at this temperature for 8 h. After that, the sample was mixed and heated at 900°C for 10 h in crucibles along with the reducing agent ͑active carbon͒.X-ray diffraction ͑XRD͒ data were collected on...

Sm 2 + ions doped KSrPO4 were prepared by high-temperature solid-state reaction method. The samples were investigated by x-ray powder diffraction, photoluminescence excitation and emission spectra, and luminescence decay measurements. After excitation into the 4f55d1 levels, the emission of Sm2+ ions showed D05→FJ7 (J=0,1,2) emission together with the broad 5d→4f emission band. The luminescence of Sm2+ ions was sensitive to the temperature. With the decreasing of the temperature, the broad 5d→4f emission band of Sm2+ ions gradually quenched, while D05→FJ7 (J=0,1,2) emission lines could be clearly detectable. Based on the luminescence properties of Sm2+ ions and structure of KSrPO4 crystal, the crystallographic sites and the energy structure correlated with 4f→5d transitions of Sm2+ ions in KSrPO4 were discussed.

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