Department of Calgary, University of Calgary, 2500 University Drive Northwest, Calgary, AB T2N 1N4, Canada.
Inorg Chem. 2011 Jan 17;50(2):647-55. doi: 10.1021/ic101846f. Epub 2010 Dec 9.
In this paper, we report the synthesis, structure and electrical properties of the perovskite-type AZn0.33+xNb0.67-xO3-δ (A = Sr or Ba; 0 ≤ x ≤ 0.08). The investigated compounds were prepared by employing the solid-state (ceramic) reaction using alkaline nitrates, zinc oxide, and niobium oxide at elevated temperatures in air. Powder X-ray diffraction (PXRD) showed the formation of disordered Zn and Nb at the B-sites of space group Pm3̅m with cubic structure and a lattice constant comparable to that of the literature. The AC impedance study showed mainly bulk contribution to the total electrical conductivity over the investigated frequency range of 0.01 Hz to 1 MHz in all the investigated atmospheres even at low temperatures, which is significantly different from that of the well-known perovskite-type B-site ordered BaCa0.33+xNb0.67-xO3-δ and the disordered acceptor-doped BaCeO3. The bulk dielectric constant determined at 500 and 700 °C in air was found to be in the range of 35-100. In air, the isothermal bulk dielectric constant seems to increase with an increasing Zn content, and a similar trend was observed for total electrical conductivity. In dry and wet H2, the electrical conductivity decreases with an increasing Zn content in AZn0.33+xNb0.67-xO3-δ, and the x = 0 member of the Ba compound exhibits the highest total conductivity of 7.2 × 10(-3) S cm(-1) in dry H2 at 800 °C. Both Sr and Ba compounds were found to be stable against the reaction with pure CO2 at 700 °C and H2O at 100 °C for a long period of time. SrZn0.33+xNb0.67-xO3-δ was found to be stable in 30 ppm H2S at 800 °C, while the corresponding Ba compound formed reaction products such as BaS (JCPDS Card 01-0757), BaS2 (JCPDS Card 21-0087), and BaS3 (JCPDS Card 03-0824).
本文报道了钙钛矿型 AZn0.33+xNb0.67-xO3-δ（A = Sr 或 Ba；0 ≤ x ≤ 0.08）的合成、结构和电学性能。所研究的化合物通过在空气中使用碱性硝酸盐、氧化锌和氧化铌在高温下采用固态（陶瓷）反应制备。粉末 X 射线衍射（PXRD）表明，在空间群 Pm3̅m 中，无序的 Zn 和 Nb 占据 B 位，形成具有立方结构和与文献相当的晶格常数的化合物。在所有研究的气氛中，即使在低温下，交流阻抗研究表明，在 0.01 Hz 至 1 MHz 的研究频率范围内，总电导率主要来自体贡献，这与众所周知的 B 位有序 BaCa0.33+xNb0.67-xO3-δ 和无序受主掺杂 BaCeO3 明显不同。在空气中于 500 和 700°C 下测定的体介电常数在 35-100 范围内。在空气中，随 Zn 含量的增加，等温体介电常数似乎增加，总电导率也表现出相似的趋势。在干燥和湿 H2 中，随 Zn 含量的增加，AZn0.33+xNb0.67-xO3-δ 的电导率降低，Ba 化合物的 x = 0 成员在 800°C 的干燥 H2 中表现出最高的总电导率 7.2×10(-3) S cm(-1)。在 700°C 下与纯 CO2 和 100°C 下与 H2O 长时间反应，Sr 和 Ba 化合物均表现出稳定性。SrZn0.33+xNb0.67-xO3-δ 在 800°C 下的 30 ppm H2S 中表现出稳定性，而相应的 Ba 化合物形成了反应产物，如 BaS（JCPDS 卡片 01-0757）、BaS2（JCPDS 卡片 21-0087）和 BaS3（JCPDS 卡片 03-0824）。
