Structural and luminescent properties of a nasicon-type phosphate (Cu0.5Mn0.25Zr2)-Mn-I-Zr-II(PO4)(3)

The phosphate (Cu0.5Mn0.25Zr2)-Mn-I-Zr-II(PO4)(3) can be obtained at 1000 d egrees C by exchange reaction in (Cu0.5Zr2)-Zr-II(PO4)(3). It crystallizes in the rhombohedral system (space group R (3) over bar) with the parameters a, 8.8352(1) Angstrom and c(h) = 22.254(5) Angstrom in the equivalent hexa gonal cell, The structure refined by the Rietveld method is typical of Nasi con-type structure. Mn2+ ions occupy partially the M-1 site, while Cu+ ions are distributed over the M-1 and M-2 sites generated by the space group. T his compound exhibits two fluorescences, occurring in the violet and orange regions and assigned respectively to isolated Cu+ and Mn2+ ions. Two other luminescences detected in the blue and green range at low temperature corr espond respectively to (Cu-2)(+) and (Cu+)(2) pairs. Efficient energy trans fer Cu+ -> Mn2+ is observed at room temperature strengthening the orange em ission of Mn2+ in the M-1 site. (C) 2000 Academic Press.