Phase transition and piezoelectricity of BaZrO3‐modified (K,Na)NbO3 lead‐free piezoelectric thin films

(K,Na)NbO3 (KNN) is a promising lead‐free ferroelectric/piezoelectric system, to which incorporating BaZrO3 can greatly enhance its piezoelectricity, but the mechanism is not clear. This work was conducted to investigate the phase transition in the BaZrO3‐modifed KNN system and its contribution to p...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2019-05, Vol.102 (5), p.2770-2780
Main Authors: Luo, Jin, Zhang, Suwei, Zhou, Zhen, Zhang, Yichi, Lee, Hyun‐Young, Yue, Zhenxing, Li, Jing‐Feng
Format: Article
Language:English
Subjects:
Barium zirconates
Ferroelectric materials
Ferroelectricity
lead‐free ceramics
Mapping
Niobates
Optimization
Organic chemistry
phase transition
Phase transitions
piezoelectric materials/properties
Piezoelectricity
Sol-gel processes
sol‐gel
Thin films
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Summary:(K,Na)NbO3 (KNN) is a promising lead‐free ferroelectric/piezoelectric system, to which incorporating BaZrO3 can greatly enhance its piezoelectricity, but the mechanism is not clear. This work was conducted to investigate the phase transition in the BaZrO3‐modifed KNN system and its contribution to piezoelectricity enhancement, using thin films with a fixed orientation and high compositional homogeneity fabricated by a sol‐gel method. Two ferroelectric‐to‐ferroelectric phase transitions are revealed, which correspond to monoclinic MC‐ MA phase transition at higher temperature and rhombohedral‐monoclinic MC phase transition at lower temperature. It is difficult to distinguish these phases in KNN‐based bulk materials, but their differences are clear when conducting high‐resolution X‐ray reciprocal space mapping (RSM) on the present thin films. Piezoresponse force microscopy experiments also revealed an interesting finding that local piezoelectricity of monoclinic phases was higher than that of rhombohedral ones in KNN‐based thin films. This work could shed insights on the fundamental understandings for the effect of the chemical doping, and offer guidance for property optimization in the KNN‐based lead‐free piezoelectrics. Phase transition and piezoelectricity were modified in (K,Na)NbO3 based lead‐free piezoelectric thin films, where the R to monoclinic MC phase transition temperature was elevated with increasing BaZrO3 doping levels and the local piezoelectricity reached the maximum value at the phase boundary.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.16172