In electrodynamics point of view equivalent bound volume charges will accumulate in the piezoelectric body in addition to the bound surface charges considering the effect of polarization gradient.

• 由于极化梯度的存在，不仅在压电体的表面上会产生等效面束缚电荷，在压电体内部同时也会有等效体束缚电荷的聚集。