Electron Structure and Piezoelectric Characteristics of PMZN System Piezoceramics

摘要

The electron structure of Pb(Zn_(1/2)Ti_(1/2))O_3(PZT), Pb(Zn_(1/3)Nb_(2/3))O_3(PZN) and Pb(Mn_(1/3)Sb_(2/3))O_3 (PMS) systems was calculated by the SCF-DV-Xα calculation method. The effects of ABO_3-type perovskite and pyrochlore ceramic electron structure on their piezoelectricity were also studied. The results showed that the ferroelectric phase is more stable than paraelectric phase and the necessary condition of stable existing ferroelectric is the mixed orbit of O2p orbit and the out layer d orbit of B-site atom. The stability of ferroelectricity can be indicated by the strength of mixed orbit. When (Zr, Ti) was substituted by Mn_(1/3)Sb_(2/3), Zn_(1/3)Nb_(2/3), if it could form tetragonal perovskite structure, the total system energy would reduce and the mixed orbit will enhance, which improves the ferroelectricity of PZT system. However, if it forms a cubic pyrochlore structure, the ferroelectricity would lose because the covalent bond strength of B-O (axial direction) and B-O (vertical axial direction) is different obviously, which lead to the system structure become unstable.