Grain boundary behaviors of ferroelectric ceramics above Curie point

In place of the Maxwell-Wagner double-layer theory for the anomalous dielectric absorption current, a novel space charge model based on experimental results for BaTiO/sub 3/ ceramics when an electric field is applied above the Curie point is proposed. This model can explain the very large charge (exceeding 1000 mu C/cm/sup 2/) stored during charging by DC field application above the Curie point and the time dependence of the discharging absorption current. When the DC field is applied at room temperature to (Sr,Ba)TiO/sub 3/ ceramics with a Curie point of -50 degrees C, the behavior corresponds to that of BaTiO/sub 3/ when a DC field is applied above the Curie point. The sample can have a giant space charge polarization. The apparent pyroelectric current was measured, with attention given to the role of grain boundaries.<
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