Crystalline phase and electrical properties of lead‐free piezoelectric KNN‐based films with different orientations
Lead‐free piezoelectric 0.915K0.5Na0.5NbO3‐0.075BaZrO3‐0.01Bi0.5Na0.5TiO3 (KNN‐BZ‐BNT) films were grown on Nb‐doped SrTiO3 substrates with different orientations. The thin films show highly preferential orientations in accordance with the orientations of single crystalline substrates. The films all exhibit a weak contrast and remarkable homogeneity in the local static out‐of‐plane piezoresponse phase images, suggesting a strong self‐polarization. Combining with the analysis of XRD‐RSM, TEM and PFM, the crystalline phase of our samples was determined to be rhombohedral, which has the spontaneous polarization along  direction. Thus, the (100)‐oriented film demonstrates the most superior piezoelectric properties. Our detailed studies on structural and electrical properties of KNN‐BZ‐BNT films further clarify the structure‐property relationship and make a step closer to use this lead‐free material for many piezoelectric applications.
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