Luminescence properties of lanthanide and transition metal ion-doped Ba2LaNbO6: detection of MnO6(8-) and CrO6(9-) clusters.
The as-prepared double-perovskite Ba(2)LaNbO(6) (space group I2/m at ambient temperatures) exhibited an unexpected well-resolved red luminescence, which was found to arise from parts-per-million impurity of Mn(4+). The ions Mn(4+) or Cr(3+) doped into this host are situated at Nb(5+) sites with slightly distorted octahedral symmetry, with the distortion greater for the case of greater charge mismatch. The Stokes luminescence spectra of the dopant ions comprise nu(3), nu(4), and nu(6) moiety mode vibronic origins, and the high vibrational frequency ratio nu(4)/nu(3) signals the stiffness of the O-M-O (M = Mn, Cr) angle in the double perovskite. The site symmetry at the La(3+) site of lanthanide ions doped into Ba(2)LaNbO(6) comprises a 2-fold axis at most. All dopant ions exhibit concentration quenching in this lattice.
Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, People's Republic of China. bhtan@cityu.edu.hk
Peter A
PA
Tanner
Zaifa
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Pan