Characterization and Rietveld Refinement of A-site deficient Lanthanum doped Barium Titanate

Ba1-xLa2x/3TiO3 (0.00 <= x <= 0.10, in a step of 0.02) ceramics have been prepared through solid state reaction route. Structural studies suggested a transition in phase from tetragonal to cubic symmetry with increase in Lanthanum content. Rietveld Refinement technique employed for investigation confirmed the same. Photoluminescence study revealed introduction of structural disorder by means of A-site vacancies and displacement of M-O bond leading to shallow defects. Optical band gap value calculated from UV-Vis spectra decreased with increase in La concentration. A drastic decrease in grain size of undoped BT was observed with introduction of La through Scanning Electron Micrographs. Dielectric studies were performed and a gradual decrease in the Curie temperature with increase in La content in coherence with structural studies was observed along with pinching effect. Normal ferroelectric character was obtained for the composition x = 0.00 to x = 0.06 while relaxor like behavior was observed for composition x >= 0.08. The composition x = 0.10 made a good Vogel-Fulcher fit. Inhomogeneity induced in the BT lattice due to 8% La doping is strong enough to make an onset of such behavior. P similar to E hysteresis loop showed a regular decrease in remnant polarization and coercive field featuring similar relaxor like behavior. (C) 2013 Elsevier B.V. All rights reserved.