Description:
Twin‐related (tetragonal (T), rhombohedral (R)) adjacent ferroelectric domains, which require a smaller energy for the rotation of the polarization vector, have been found to occur in lead zirconate titanate type piezoceramics at the morphotropicphase boundary, explaining the triplet splitting observed in electron diffraction patterns. The values of elastically stored energy density in the walls of the twinning domains are estimated, and a packing model of the ferroelectric domain structure as a T1RT2RT1…succession is proposed to explain the coexistence of the two ferroelectric phases in the morphotropicphase boundary region. A crystallographic analysis of the transformation from the paraelectric to the ferroelectric phase is performed on the basis of martensite transformation theory. The calculated results are in good agreement with the observed transmission electron microscopy data. In particular, the crystallography and morphology of the “herringbone” domain structure, often observed in piezoelectrio ceramics, are well explained by this analysis.