Lithium-lanthanum titanate, Li 0•29 La 0•57 TiO 3 , is prepared by solid-state reaction method and it is furnace-cooled to room temperature. X-ray diffraction results indicated that the compound has tetragonal perovskite-like structure and the lattice parameters are determined as a = 3•8714 Å and c = 7•7370 Å. The average grain size is found to be 5 μm from SEM micrograph. The analysis of FTIR and Raman spectra of the sample supported tetragonal structure inferred from XRD data. The impedance spectrum of the sample is separated into bulk and grain boundary parts by analysing the impedance data. The high bulk ionic conductivity is reported as 1•12 × 10 −3 S cm −1 at room temperature. D.C. conductivity measurements indicate that the compound is a good ionic conductor.

We present first principles calculations of the electronic, structural and optical properties of the cubic perovskite CsSrF 3 by using the full potential linearized augmented plane wave (FP-LAPW) plus local orbitals method with generalized gradient approximation (GGA) in the frame work of density functional theory. The calculated lattice constant is in a good agreement with the experimental result. The electronic band structure shows that the fundamental band gap is wide and direct at Γ point. The contribution of the different bands was analyzed from the total and partial density of states curves. The charge density plots show strong ionic bonding in Cs-F, ionic and weak covalent bonding between Sr and F. The calculated optical spectra viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of 0-30 eV.

The structural and optoelectronic properties of cubic perovskite RbPbF 3 are calculated using all electrons full potential linearized augmented plane wave (FP-LAPW) method. The calculated lattice constant is in good agreement with the experimental result. The calculated band structure shows a direct band gap of 3•07 eV. The contribution of different bands is analysed from the total and partial density of state curves. We identified hybridization of Pb s, Pb p states with F p states in the valence bonding region. Calculations of the optical spectra, viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss are performed for the energy range of 0-30 eV. Based on the direct bandgap, as well as other optical properties of the compound, it is predicted that this material is useful for vacuum-ultraviolet-transparent (VUV-transparent) applications.