锶镁共掺对Na0.5Bi0.5TiO3氧离子导体电学性能的影响分析

Investigation on electrical performance of Sr,Mg, co-doped Na0.5Bi0.5TiO3 oxide ion conductor

通过固相反应法制备单一结构的锶镁共掺的Na0.5Bi0.48Sr0.02Ti0.98Mg0.02O2.97氧离子导体,利用交流阻抗谱和内耗温度谱分别研究锶镁共掺对Na0.5Bi0.5TiO3材料晶粒电导率及氧离子扩散的影响。在593K时,Na0.5Bi0.48Sr0.02Ti0.98Mg0.02O2.97材料的晶粒电导率可以达到5.31×10^-4S/cm,比母体Na0.5Bi0.5TiO3材料在同温度下的晶粒电导率高一个数量级,甚至超过了Na0.5Bi0.5Ti0.98Mg0.02O2.98样品在673K温度下的晶粒电导率。在锶镁共掺的Na0.5Bi0.48Sr0.02Ti0.98Mg0.02O2.97材料中观察到一个氧弛豫内耗峰,其弛豫参数为:E=0.85eV,τ0=7.4×10^-14s。结合弛豫参数和结构分析,Sr^2+的掺杂在一定程度上可以增大氧离子扩散的自由体积,较大的自由体积、较高的可动氧空位浓度和较好的氧空位可动性是NBT-SrMg2样品晶粒电导率相较于NBT-Mg2样品大幅提高的主要原因。

Na 0.5 Bi 0.48 Sr 0.02 Ti 0.98 Mg 0.02 O 2.97 compound was synthesized by solid-state reaction. AC impedance and internal friction spectroscopy were employed to study the electrical performance and oxgyen ion diffusion in the Sr,Mg-co-doped Na 0.5 Bi 0.5 TiO 3 compounds. The grain conductivity of Na 0.5 Bi 0.48 Sr 0.02 Ti 0.98 Mg 0.02 O 2.97 sample can reach 5.31×10^-4 S/cm at 593 K, an order of magnitude higher than that of the Na 0.5 Bi 0.5 TiO 3 compound at the same temperature and exceeding the grain conductivity of Na 0.5 Bi 0.5 Ti 0.98 Mg 0.02 O 2.98 sample at 673K. An internal friction relaxation peak was observed. The relaxation parameters can be calculated, E = 0.85eV and τ 0= 7.4×10^-14 s. Judging from the relaxation parameters and structural analysis, the Sr^2+ dopant can amplify the specific free volume. Compared with the Na 0.5 Bi 0.5 Ti 0.98 Mg 0.02 O 2.98 sample, the substantial increase of the grain conductivity for Na 0.5 Bi 0.48 Sr 0.02 Ti 0.98 Mg 0.02 O 2.97 sample may be derived from the larger specific free volume, higher mobile oxygen vacancy content and better oxygen vacancy mobility.