Optimizing K0.5Na0.5NbO3 Single Crystal by Engineering Piezoelectric Anisotropy

• Published in: Nanomaterials (Basel, Switzerland) Vol. 11; no. 7; p. 1753
• Main Authors: Li, Weixiong, Chen, Chunxu, Xie, Guangzhong, Su, Yuanjie
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 05.07.2021; MDPI
• Subjects: Anisotropy; Communication; Cooling; Crystals; Energy; Ferroelectricity; Internet of Things; K0.5Na0.5NbO3; Lead free; Optimization; Orthorhombic phase; phase; Phase transitions; piezoelectric; Piezoelectric ceramics; Single crystals; Switches; Temperature; Temperature dependence
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano11071753

K0.5Na0.5NbO3 is considered as one of the most promising lead-free piezoelectric ceramics in the field of wearable electronics because of its excellent piezoelectric properties and environmental friendliness. In this work, the temperature-dependent longitudinal piezoelectric coefficient d33* was investigated in K0.5Na0.5NbO3 single crystals via the Landau–Ginzburg–Devonshire theory. Results show that the piezoelectric anisotropy varies with the temperature and the maximum of d33max* deviates from the polar direction of the ferroelectric phase. In the tetragonal phase, d33maxt* parallels with cubic polarization direction near the tetragonal-cubic transition region, and then gradually switches toward the nonpolar direction with decreasing temperatures. The maximum of d33o* in the orthorhombic phase reveals a distinct varying trend in different crystal planes. As for the rhombohedral phase, slight fluctuation of the maximum of d33r* was observed and delivered a more stable temperature-dependent maximum d33maxr* and its corresponding angle θmax in comparison with tetragonal and orthorhombic phases. This work not only sheds some light on the temperature-dependent phase transitions, but also paves the way for the optimization of piezoelectric properties in piezoelectric materials and devices.