Electron microscopy
 
Direction of Spontaneous Polarization in Ferroelectrics
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Ferroelectric substances normally present separate regions called domains that have different spontaneous polarization directions. The number of distinct spontaneous polarization directions depends on its point group symmetry.

For perovskite-like structures, the periodic O–B ion–O chains are effective in ferroelectric characteristics so that the direction of the spontaneous polarization is parallel to the a–b plane of the structures because this plane contains the periodic O–B ion–O chains. However, no spontaneous polarization exists along the c-axis because of the lack of periodic symmetry in the O–B ion–O chain.

 

 

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