Luminescence properties of lanthanide and transition metal ion-doped Ba₂LaNbO₆ : Detection of MnO₆^8- and CrO₆^9- clusters

The as-prepareddouble-perovskite Ba₂LaNbO₆ (space group l2/mat ambient temperatures) exhibited an unexpected well-resolved red luminescence, which was found to arise from parts-per-million impurity of Mn⁴⁺. The ions Mn⁴⁺ or Cr³⁺ doped into this host are situated at Nb⁵⁺ 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 v₃, v₄, and V₆ moiety mode vibronic origins, and the high vibrational frequency ratio v₄/v₃ signals the stiffness of the O-M-O (M = Mn, Cr) angle in the double perovskite. The site symmetry at the La³⁺ site of lanthanide ions doped into Ba₂LaNbO ₆ comprises a 2-fold axis at most. All dopant ions exhibit concentration quenching in this lattice. © 2009 American Chemical Society.