Dramatic Influence of A-Site Nonstoichiometry on the Electrical Conductivity and Conduction Mechanisms in the Perovskite Oxide Na0.5Bi0.5TiO3

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• 作者：Ming Li ; Huairuo Zhang ; Stuart N. Cook ; Linhao Li ; John A. Kilner ; Ian M. Reaney ; Derek C. Sinclair
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：January 27, 2015
• 年：2015
• 卷：27
• 期：2
• 页码：629-634
• 全文大小：327K
• ISSN：1520-5002

文摘

Recently, there has been considerable interest in the perovskite phase Na_0.5Bi_0.5TiO₃ (NBT) as a promising lead-free piezoelectric material. Here we report low levels of Na nonstoichiometry (卤2 atom % on the A-site) in the nominal starting composition of NBT ceramics can lead to dramatic changes in the magnitude of the bulk (grain) conductivity (蟽_b) and the conduction mechanism(s). Nominal starting compositions with Na excess exhibit high levels of oxide-ion conduction with 蟽_b 鈭?2.2 mS cm^鈥? at 600 掳C and an activation energy (E_a) < 1 eV whereas those with Na deficiency are dielectrics based on intrinsic electronic conduction across the band gap with 蟽_b 鈭?1.6 渭S cm^鈥? at 600 掳C and E_a 鈭?1.7 eV. Drying of reagents, especially Na₂CO₃, changes the starting stoichiometry slightly due to a small amount of adsorbed moisture in the raw materials but influences significantly the electrical properties. This demonstrates the bulk electrical properties of NBT to be highly sensitive to low levels of A-site nonstoichiometry and reveals how to fine-tune the nominal starting composition of NBT ceramics to suppress leakage conductivity for piezoelectric and high temperature capacitor applications.