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材料物理性能4.ppt

发布:2017-01-08约字共6页下载文档
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Total Induced Dipole Moment Ionic Electric Orinetational Polarization Complex Relative Permittivity Dielectric Loss per Unit Volume Capacitance per unit volume 1 Piezoelectricity: Certain crystals, become polarized when they are mechanically stressed. 2. Certain crystals are permanently polarized even in the absence of an applied field. The crystal already possesses a finite polarization vector due to the separation pf positive and negative charges in the crystal. 3. A temperature change δT induces a change δP in the polarization of the crystal. This is called pyroelectricity * Dipole Moment p = Qa Polarizability p = ?E Pav=αEloc pav = ?e Eloc + ?i Eloc + ?d Eloc Maximum energy per unit volume Piezoelectricity, Ferroelectricity, and Pyroelectricity *
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