Na0.5Bi8.5Ti7O27共生铋层状压电陶瓷的电导和弛豫机制研究

Conduction and Relaxation Mechanism of Na0.5Bi8.5Ti7O27 Inter-growth Bismuth Layer-structured Piezoelectric Ceramics

铋层状压电陶瓷在高温电子器件领域中占有十分重要的,其高温电导和弛豫行为对陶瓷的电学性能有着直接影响。本文采用固相法制备了Na0.5Bi8.5Ti7O27共生铋层状无铅压电陶瓷,通过X射线衍射、X射线光电子能谱以及高温阻抗等测试手段,系统地研究了陶瓷内部的缺陷与其电导和弛豫的内在联系。结构分析表明陶瓷样品形成了单一的铋层状结构,其内部存在少量的Ti3+离子;阻抗分析表明在400-620℃温度范围内,电导机制源于氧空位一级电离的贡献,其电导激活能为1.11 eV,表现为单一的电导机制,而弛豫机制在相同的温度范围内表现出两种不同机制,在400-540℃温度范围内,弛豫机制源于氧空位的短程跃迁,其弛豫激活能为1.12 eV,在540-620℃温度范围内,弛豫机制归于Ti离子的变价,其弛豫激活能为0.73 eV。

Bismuth layer-structured piezoelectric ceramics play an important role in the field of high temperature electronic devices,whose conduction and relaxation mechanism at high temperatures directly influence their electrical properties.The internal defects of Na0.5Bi8.5Ti7O27 inter-growth bismuth layer-structured lead-free piezoelectric ceramics synthesized with solid-state reactions and the intrinsic connection between the conduction and relaxation mechanism have been systematically studied by using X-ray diffraction(XRD),X-ray photoelectric spectroscopy(XPS)and impedance spectra.It was found that the ceramic samples possessed a single bismuth layer-structure with a trace of Ti3+in the lattice.According to impedance analytic results,the conduction mechanism of the samples in the temperature range of 400-620℃ was closely linked to the first ionization of oxygen vacancies with a DC conductivity activation energy of 1.11 eV However,the relaxation in the above temperature range followed two mechanisms,corresponding to short range transition of oxygen vacancies and valence change of titanium ions,in the temperature regions of 400-540℃ and 540-620℃,with relaxation activation energies of 1.12 eV and 0.73 eV respectively.