Microstructure Study of BaTiO3–Ho2O3–MgO–SiO2-Based Ceramics Using Convergent Beam Electron Diffraction Analysis

概要

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The mechanism of Curie temperature ($T_{\text{C}}$) elevation in BaTiO3–Ho2O3–MgO–SiO2-based X8R ceramics was investigated in terms of the variations in the lattice parameters of individual grains using convergent beam electron diffraction analysis. Three sintered samples with different values of $T_{\text{C}}$ depending on Ho and Si concentrations were observed to have a lattice parameter gradient even in the grain core of almost pure BaTiO3 as well as in the grain shell with a chemical gradient. Interestingly, the sample with a higher $T_{\text{C}}$ exhibited a flatter gradient of the lattice parameter in the grain core, implying less prominent development of compressive stress. It is suggested that the incorporation of a high Ho concentration into the grain shell has significant effects on the relaxation of the compressive stress mainly arising from ferroelectric phase transition. This results in the shifting of $T_{\text{C}}$ toward a higher value.
2009-09-25