Space Charge Effect in Lead Zirconate Titanate Ceramics Caused by the Addition of Impurities

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Abstract
Lead zirconate titanate ceramics containing metal oxides as impurities are subjected to poling, in order to give rise to piezoelectric activity, at various temperatures. Impurities contained in the ceramics are found to be divided into three groups according to their effects on poling temperatures. (1) When the amounts are small, piezo-electric activity is lowered by poling at low temperatures, but not so when the amounts increase. (2) Irrespective of the amounts the activity is lowered by poling at low temperatures. (3) Irrespective of the amounts the activity is independent of poling temperatures. Lowering of piezoelectric activity is accompanied by an increase of specific resistivity. The lowering is explained by the effect of space charge which is generated by the addition of impurities. An empirical formula on poling efficiency is derived in terms of space charge and specific resistivity of the ceramics.