Ferroelectric Domain Structures and their Morphology Evolution in Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 Piezoelectric Ceramics Modified by Bismuth and Zinc Substitutions

Abstract

Ferroelectric domain structures and their morphology evolution in the Bi‐ and Zn‐modified (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)x(ZrσTi1−σ)1−xO3 piezoelectric ceramics (0.20≤x≤0.60 and 0.10≤σ≤0.60) are investigated as a function of the relaxor Pb(Ni1/3Nb2/3)O3 content and the Zr/(Zr+Ti) ratio (σ) by transmission electron microscopy and selected area electron diffraction, and followed by a complete analysis of the nature of the domain walls based on the predicated twinning planes for the formation of domains in these piezoelectric ceramic systems. A systematic variation in the domain morphology was observed as the compositions move from the ferroelectric tetragonal (FT) to pseudocubic (Fpc) phases, and then to the rhombohedral (FR) phase. Wedged‐shaped domains with misoriented {110} domain walls and mixed with herringbone‐like configuration are the main features of the ferroelectric domains in the FT and Fpc phases, whereas in the compositions near the morphotropic phase boundary (MPB) between the Fpc and FR phases, the characteristic feature of the ferroelectric domains is an intricate domain structure exhibiting a fluctuating mottled contrast. However, the domain boundaries in the FR phase exhibit a wavy character. The domain feature for the compositions at/near the MPB between the FT and FR phases with high property coefficients is a 90° domain texture mixed with an intricate domain structure. The different domain configurations observed in the FT and FR phases are due to their different accommodations of local elastic strain fields. The piezoelectric soft behavior and a normal‐relaxor ferroelectric behavior transition observed in this piezoelectric ceramic system are closely related to the above domain morphology evolution as increasing the PNN content or the Zr/(Zr+Ti) ratio.