Crystal structure modeling, electrical and microstructural characterization of manganese doped barium zirconium titanate ceramics

Three ceramic perovskite phases, BaTi0.90Mn0.1O3 (MnBT), BaTi0.94Zr0.05Mn0.01O3 (MnBTZ-5) and BaTi0.89Zr0.10Mn0.01O3 (MnBTZ-10), were synthesized by a ceramic route at 1050 degrees C, and crystallize with cubic symmetry (space group Pm (3) over barm). Their crystal structures have been refined by Rietveld analysis of powder X-ray diffraction data. The structure refinement converged to satisfactory values of the Rietveld parameters, R-p and R-wp, and goodness of fit. The lattice parameters, structure factors, bond lengths and bond angles have been calculated from General Structure Analysis System software (GSAS). Particle size, morphology and the lattice fringes of the sintered powders have been characterized by scanning and transmission electron microscopy. The particle size was also determined from the XRD pattern using Scherrer's equation. Their dielectric behavior has been investigated in the a.c. frequency range 42 Hz-5 MHz at temperatures between 25 and 240 degrees C. The fine grained phase MnBTZ-10 shows a frequency dependent broad dielectric constant. A dielectric maximum has been observed at 25 degrees C and 80 Hz frequency. (C) 2011 Elsevier Ltd. All rights reserved.