The electric field-induced phase transitions in Li-modified Na0.5K0.5NbO3 at the polymorphic phase boundary (PPB) were observed using in situ X-ray diffraction. The ratio of monoclinic to tetragonal phase fraction was used as an indicator of the extent and reversibility of the phase transitions. The reversibility of the phase transition was greater in compositions further from the PPB. These results demonstrate that the field-induced phase transition is one of the origins of high piezoelectric properties in lead-free ferroelectric materials.

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This study investigates the effect of CoO and Fe2O3 dopant on phase, microstructure and ferroelectric properties of BCZT ceramics with the formula of Ba0.85Ca0.15Zr0.1(Ti1‐xCox)0.9O3 and Ba0.85Ca0.15Zr0.1(Ti1‐xFex)0.9O3 where x = 0, 0.01, and 0.03. The XRD patterns presented that the pure perovskite phases are observed regardless of the amount of CoO and Fe2O3 added. Rietveld analysis shows that the tetragonal phase is observed in all patterns and the unit cell volume slightly expanded by the CoO addition while it is distorted with increasing Fe2O3 addition. The average grain sizes decreased upon CoO and Fe2O3 addition. It is found that the doping of CoO and Fe2O3 caused the transition temperature to shift to lower temperature. The optimum ferroelectric and dielectric properties can be achieved for the BCZT‐0.01Co ceramics. This study shows that while small doping with Co and Fe can enhance different properties of BCZT with lower processing temperature, the properties should be further optimized by chemical modification.

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Lead zirconate titanate (PZT) is one of the most commonly used piezoelectric ceramics. The major causes of its electrical fatigue are suggested to be domain pinning and cracking. However, their contributions to fatigue have never been quantitatively compared. This study focuses on the electrical fatigue‐induced microstructure damage in the near‐electrode regions of PZT and uses a refatigue method to determine quantitatively the contribution of the cracking mechanism to electrical fatigue. It is shown that during bipolar electrical cycling, a large number of cracks are initiated in the samples, and the cracking is particularly concentrated in the near‐electrode regions. So the loss of piezoelectric properties can be partially restored by removing such regions. For a particular fatigue stage, the cracking mechanism contributes significantly more to the electrical fatigue than the domain pinning mechanism.

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