B位取代PZT体系的电子结构与压电特性研究

采用自洽场离散变分Xα计算方法,分别计算了Pb(Zr1/2Ti1/2)O3(简称PZT)、Pb(Zn1/3Nb2/3)O3(简称PZN)、和Pb(Mn1/3Sb2/3)O3(简称PMS)体系的电子结构,研究了钙钛矿结构与烧绿石结构陶瓷的电子结构对压电性能的影响.结果表明,PZT铁电相较顺电相稳定,O的2p轨道与B位原子的最外层d轨道的杂化是铁电性的必要条件,杂化的强弱可表明铁电性的强弱;Mn1/3Sb2/3、Zn1/3Nb2/3取代(Zr, Ti)若生成四方钙态矿结构,体系总能量降低、轨道杂化增强,可以提高PZT体系的铁电性能,若生成立方烧绿石结构,由于B-O(//轴向)与B-O(⊥轴向)共价键强度差别太大,造成体系结构的不稳定,将导致铁电性的丧失.

Electron Structure and Piezoelectric Characteristics of PZT System Piezoceramics

The structures of Pb(Zr1/2Ti1/2)O3(PZT), Pb(Zn1/3Nb2/3)O3(PZN) and Pb(Mn1/3Sb2/3)O3(PMS) system were respectively calculated by using the SCC-DV-X a calculation method and the effects of ABO3 type perovskite and pyrochlore ceramic electric structure on the piezoelectricity were studied. The results show that the ferroelectric phase is more stable than paraelectric phase, the necessary condition of ferroelectricity is the hybrid orbit of O2p orbit and the outset layer d orbit of B position atom. The strength of hybrid orbit indicates the strength of ferroelectricity. When Mn1/3Sb2/3, Zn1/3Nb2/3 substitute the position of (Zr, Ti), if the tetragonal perovskite structure obtained then the total system energy will be reduced and the hybrid orbit will be enhanced, so the ferroelectricity of PZT system will increase; if the cubic pyrochlore structure obtained, the ferroelectricity will lose because the covalent bond strength of B-O (axial direction) and B-O (vertical axial direction) is different widely, which leads to the system structure unstable.