Donor-doping and reduced leakage current in Nb-doped Na0.5Bi0.5TiO3
Donor-doping and reduced leakage current in Nb-doped Na0.5Bi0.5TiO3
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DOI：
10.1063/1.4914509
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发表时间：
2015-03
影响因子：
4
通讯作者：
M. Li;Linhao Li;J. Zang;D. Sinclair
中科院分区：
文献类型：
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作者：
M. Li;Linhao Li;J. Zang;D. Sinclair
钛酸盐基钙钛矿氧化物中所谓的低水平“施主掺杂”，例如（Ba，Sr）TiO3中的Ba、Sr中的La和Ti中的Nb，可以显着降低这些典型（d0）介电材料的电阻率，并将应用领域扩展到正温度系数电阻器、热电材料、作为薄膜基材的导电晶片以及固体氧化物燃料电池阳极材料。在这里，我们展示了著名的无铅压电钙钛矿氧化物 Na 0.5Bi0.5TiO3 (NBT) 中 Ti 位点上的低水平 Nb 掺杂 (≤1 at.%) 产生完全不同的行为，从而获得更高的电阻率，因此表明不同的施主掺杂（取代）机制。传导机制发生了从活化能 (Ea) <0.9 eV 的未掺杂 NBT 中的氧离子到 0.5-1 at 的电子（带隙）传导的转变。 % Nb 掺杂 NBT，Ea ∼ 1.5–1.8 eV。这表明有必要进行进一步系统的掺杂研究，以阐明 NBT 的缺陷化学性质，NBT 与 (Ba,Sr)TiO3 的缺陷化学性质明显不同。如果要大规模生产用于商业应用的 NBT 材料，就需要了解这种缺陷化学性质。这项研究还说明了 d0 钛酸盐钙钛矿家族中存在不同的供体掺杂机制。
Low levels of so-called “donor-doping” in titanate-based perovskite oxides such as La for Ba, Sr, and Nb for Ti in (Ba, Sr)TiO3 can significantly reduce the resistivity of these typical (d0) dielectric materials and expand application areas to positive temperature coefficient resistors, thermoelectrics, conductive wafers as thin film substrates, and solid oxide fuel cell anode materials. Here, we show low levels of Nb-doping (≤1 at. %) on the Ti-site in the well-known lead-free piezoelectric perovskite oxide Na 0.5Bi0.5TiO3 (NBT) produces completely different behaviours whereby much higher resistivity is obtained, therefore indicating a different donor-doping (substitution) mechanism. There is a switch in conduction mechanism from oxygen-ions in undoped NBT with an activation energy (Ea) of <0.9 eV to electronic (band gap) conduction in 0.5–1 at. % Nb-doped NBT with Ea ∼ 1.5–1.8 eV. This demonstrates the necessity of further systematic doping studies to elucidate the defect chemistry of NBT which is clearly different to that of (Ba,Sr)TiO3. This defect chemistry needs to be understood if NBT-based materials are going to be manufactured on a large scale for commercial applications. This study also illustrates different donor-doping mechanisms to exist within the family of d0 titanate-based perovskites.