title: Crystallographic site swapping of La3+ ion in BaA'LaTeO6 (A' = Na, K, Rb) double perovskite type compounds: diffraction and photoluminescence evidence for the site swapping.
abstract: Double perovskite type compounds of the formula BaA'LaTeO6 (A' = Na, K, Rb) were synthesized by solid state route and their crystal structures were determined by Rietveld analysis using powder X-ray diffraction and neutron diffraction data. Na compound crystallizes in the monoclinic system with P2₁/n space group whereas, K and Rb compounds crystallize in Fm3m space group. All the three compounds show rock salt type ordering at B site. Crystal structure analysis shows that La ion occupies A site in Na compound whereas, it occupies B site in K and Rb compounds according to the general formula of AA'BB'O6 for a double perovskite type compound. Effect of this crystallographic site swapping of the La ion was also observed in the photoluminescence study by doping Eu(3+) in La(3+) site. The large decrease in the intensity of the electric dipole ((5)D0-(7)F2) transition in the Rb compound compared to the Na compound indicates that Eu(3+) ion resides in the centrosymmetric octahedral environment in the Rb compound.
authors.affiliation: Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India. sksali@barc.gov.in.
authors.forename: R
authors.initials: R
authors.lastname: Phatak
authors.forename: S K
authors.initials: SK
authors.lastname: Gupta
authors.forename: K
authors.initials: K
authors.lastname: Krishnan
authors.forename: S K
authors.initials: SK
authors.lastname: Sali
authors.forename: S V
authors.initials: SV
authors.lastname: Godbole
authors.forename: A
authors.initials: A
authors.lastname: Das