Effect of biased electric field on the properties of ferroelectric-dielectric composite ceramics with different phase-distribution patterns

- Three kinds of phase-distribution patterns were formed by prolonging the milling time.
- The dielectric permittivity shows a significant variation with the applied DC bias field.
- TC was increased while dielectric peaks were suppressed and broadened as increasing the DC.
- The trend of tunability slightly lags behind the change of dielectric permittivity.
- The result can be rationalized in terms of the phase-distribution patterns.

Three series of composite ceramic systems including 85 vol% Ba0.5Sr0.5TiO3 - 15 vol% MgO, 78 vol% Ba0.45Sr0.55TiO3 - 22 vol% Mg2TiO4 and 48 vol% Ba0.4Sr0.6TiO3 - 52 vol% BaWO4 were synthesized by solid-state reaction. The diphase ceramics transformed from layer-like pattern and column-like one to final sphere-like one with prolonging the milling time of raw materials from 5 min to 24 h. The dielectric permittivity and tunability of diphase ceramics were improved significantly by the change of phase-distribution patterns. The dielectric permittivity of composite system shows a variation with the applied DC bias field. The Curie temperature was increased while the dielectric peaks were suppressed and broadened as increasing the DC bias field. The tunability presents a maximum value near the ferroelectric-paraelectric phase transition point. The trend of tunability slightly lags behind the change of dielectric permittivity. The comprehensive performance of the material is improved with the increase of the uniformity. However, the quality factor Q values were strongly deteriorated. This result is contrary to the 'intuitive belief'―a prolonged milling time should improve the Q values due to the well uniformity of diphase distribution.

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