Ferroelectric Domain Structures and their Morphology Evolution in Pb(Ni 1/3 Nb 2/3 )O 3 –PbZrO 3 –PbTiO 3 Piezoelectric Ceramics Modified by Bismuth and Zinc Substitutions

Ferroelectric domain structures and their morphology evolution in the Bi‐ and Zn‐modified (Pb 0.985 Bi 0.01 )(Ni 1/4 Zn 1/12 Nb 2/3 ) x (Zr σ Ti 1−σ ) 1− x O 3 piezoelectric ceramics (0.20≤ x ≤0.60 and 0.10≤σ≤0.60) are investigated as a function of the relaxor Pb(Ni 1/3 Nb 2/3 )O 3 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 ( F T ) to pseudocubic ( F pc ) phases, and then to the rhombohedral ( F R ) 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 F T and F pc phases, whereas in the compositions near the morphotropic phase boundary (MPB) between the F pc and F R phases, the characteristic feature of the ferroelectric domains is an intricate domain structure exhibiting a fluctuating mottled contrast. However, the domain boundaries in the F R phase exhibit a wavy character. The domain feature for the compositions at/near the MPB between the F T and F R phases with high property coefficients is a 90° domain texture mixed with an intricate domain structure. The different domain configurations observed in the F T and F R 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.