Effect of core shell morphology on dielectric properties of Zr doped BaTiO/sub 3/

The core-shell grains and lattice structure in Zr-modified BaTiO/sub 3/ were characterized. Through TEM (transmission electron microscopy), CBED (convergent-beam electron diffraction), and EDS (dispersive X-ray spectroscopy) techniques, the shells were identified as diffuse regions of pseudocubic structure surrounding a tetragonal BaTiO/sub 3/ core. Grain morphology and developed internal stresses in BaTiO/sub 3/-based high dielectric materials are shown to be a dominant factor in the development and stability of the high dielectric properties. Core-shell grains were formed in BaTiO/sub 3/ with ZrO/sub 2/ doping, upon sintering in the range 1300 degrees C-1320 degrees C. A diffused boundary phase led to high internal stresses, suppression of T/sub c/, a distribution of Curie points, and a flattened permittivity peak. The internal stress was found to be an accurate basis for estimating the permittivity response to temperature. The stability of these highly stressed samples was also found to be improved as the concentration of core-shell grains increased. Under controlled processing parameters, therefore, significantly enhanced dielectric properties can be achieved.<
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