Dielectric Properties of BaTiO3-Based Ceramics under High Electric Field

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The dielectric properties under a high electric field (ac-field) of BaTiO3-based ceramics with core grains, shell grains and core-shell grains were compared with those of multilayer ceramic capacitors (MLCCs) with these three kinds of grains. The MLCCs with the X7R specification had a core-shell structure, and the relative dielectric permittivity ($\varepsilon_{\text{r}}$) of the dielectric layers in the MLCCs increased with increasing ac-field. Similar behavior was observed in the MLCCs consisting of only cores, indicating that the core predominantly determined the dielectric properties of MLCCs under high ac-fields. The dielectric properties of MLCCs and ceramic plates consisting of only shell grains showed that the shell was the relaxor ferroelectrics. A slight change in the shell composition yielded a large shift of the peak temperature of $\varepsilon_{\text{r}}$. The shell improved the temperature stability of $\varepsilon_{\text{r}}$ at low temperatures under low ac-fields. In a ceramic plate with relatively large BaTiO3 grains (approximately 3 $\mu$m), the maximum $\varepsilon_{\text{r}}$ was observed at a moderate ac-field, which was explained from the electric displacement vs electric field hysteresis curves of ferroelectric BaTiO3. The MLCCs and ceramics plates with fine BaTiO3 grains (0.4 to 0.5 $\mu$m) showed similar dielectric behavior to the MLCC with the core-shell structure. The size effect of BaTiO3 played an important role in determining the temperature stability of $\varepsilon_{\text{r}}$. For future MLCCs with very thin dielectric layers, a microstructure with fine BaTiO3 grains and grain boundary layers of the shell was proposed.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
2002-11-30

Dielectric Properties of BaTiO3-Based Ceramics under High Electric Field

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