Piezoelectricity in K1-xNaxNbO3： First-principles calculation

• Published in: 中国物理B：英文版 2015-05 (5), p.300-304
• Main Author: 李强 张锐 吕天全 郑立梅
• Format: Article
• Language: English
• Subjects: KNbO3; 偏振旋转; 压电响应; 压电性能; 压电系数; 弹性性质; 数据一致; 第一原理计算
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/24/5/053101

The piezoelectric properties of K1-xNaxNbO3 are studied by using first-principles calculations within virtual crystal approximation. To understand the critical factors for the high piezoelectric response in K1-xNaxNbO3, the total energy, piezoelectric coefficient, elastic property, density of state, Born effective charge, and energy barrier on polarization rotation paths are systematically investigated. The morphotropic phase boundary in K1-xNaxNbO3 is predicted to occur at x = 0.521, which is in good agreement with the available experimental data. At the morphotropic phase boundary, the longitudinal piezoelectric coefficient d33 of orthorhombic K0.5Na0.5NbO3 reaches a maximum value. The rotated maximum of d＊33 is found to be along the 50° direction away from the spontaneous polarization （close to the [001] direction）. The moderate bulk and shear modulus are conducive to improving the piezoelectric response. By analyzing the energy barrier on polarization rotation paths, it is found that the polarization rotation of orthorhombic K0.5Na0.5NbO3 becomes easier compared with orthorhombic KNbO3, which proves that the high piezoelectric response is attributed to the flattening of the free energy at compositions close to the morphotropic phase boundary.