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.

An efficient gel-combustion synthesis of visible light emitting barium zirconate perovskite nanoceramics: Probing the photoluminescence of Sm 3+ and Eu 3+ doped BaZrO 3

“…We wanted to the probe the site occupancy of Eu 3 þ and Sm 3 þ through time resolved photoluminescence spectroscopy. Eu 3 þ is often used as a structural probe [41][42][43][44][45][46][47], because of the (a) relative simplicity of its energy-level structure and the fact that it possesses non-degenerate ground ( 7 F 0 ) and excited ( 5 D 0 ) states and (b) absorption and emission spectra of this ion show marked dependence on its site symmetry in the host material.The orange emission (590-600 nm) of Eu 3 þ due to the magnetic dipole transition (MDT) 5 D 0 -7 F 1 is not affected much by the site symmetry, because they are parity-allowed, while the red emission ( $ 610-630 nm) due to the electric dipole transition (EDT) of 5 D 0 -7 F 2 , being hypersensitive, is affected by the site symmetry of Eu 3 þ ion. In a crystal site inversion symmetry the EDT are strictly forbidden and the MDT are usually the dominant emission line.…”

Energy transfer dynamics and luminescence properties of Eu3+ in CaMoO4 and SrMoO4

“…[12][13][14][15][16][17][18]. It is considered as a special ion because of (a) non-degenerate 7 F 0 ground level and non-overlapping 2S+1 L J multiplets (b) emission from 5 D 0 level is the most intense one which is not split into sublevels due to crystal field and (c) in a crystal site with centre of inversion the electric dipole transition (EDT) are strictly forbidden and the magnetic dipole transition (MDT) is usually the most intense and in a site without centre of inversion EDT is usually the strongest emission line, because transition ∆J= ±2 are hypersensitive to small deviation from inversion symmetry.…”

Europium Luminescence as a Structural Probe: Structure‐Dependent Changes in Eu3+‐Substituted Th(C2O4)2·xH2O (x = 6, 2, and 0)

“…Among the lanthanide ions, Eu 3+ ions are often used as structural probes [10][11][12][13][14] because of their relatively simple energy-level structure and nondegenerate ground ( 7 F 0 ) and 4429 from symmetric to highly distorted with the decrease in water content. The relative intensity ratios (I) of the EDT to MDT for x = 6, 2, and 0 are 2.36, 3.32, and 4.23, respectively.…”