La_2(Mo_(1-x)V_x)_2O_(9-α)的制备及其导电性

Synthesis and Electrical Properties of La_2(Mo_(1-x)V_x)_2O_(9-α)

采用固相法合成了系列陶瓷样品La2(Mo1-xVx)2O9-α(x=0.02,0.04,0.06,0.08).粉末X射线衍射(XRD)结果表明样品具有单一立方相La2Mo2O9结构.采用气体浓差电池、电化学阻抗等电化学方法研究了陶瓷样品在823-1123K下的导电特性.系列陶瓷样品已完全抑制La2Mo2O9母体在853K附近的相变;各样品在干燥及湿润氧气气氛中几乎为纯氧离子导体,质子导电性可忽略不计;氧离子电导率σ随掺杂离子浓度的变化为σ(x=0.02)<σ(x=0.08)<σ(x=0.06)<σ(x=0.04),这与晶胞自由体积大小的次序完全一致,x=0.04样品具有最高的氧离子电导率0.051S·cm-1;氧分压与电导率的关系表明,在高氧分压气氛中样品是纯的氧离子导体,在低氧分压气氛中是氧离子与电子的混合导体.

A series of ceramic samples La2（Mo1-xVx）2O9-α （x = 0.02, 0.04, 0.06, 0.08） were synthesized by a solid-state reaction method. X-ray powder diffraction （XRD） patterns show that all the ceramic samples have a single cubic structure. The conductive properties of the ceramic samples were investigated using gas concentration cells and electrochemical impedance spectroscopy at 823-1123 K. All the samples have completely suppressed the phase transition, which occurs in La2Mo2O9 at around 853 K. The ceramic samples are almost pure oxide-ionic conductors and do not possess the protonic conduction in dry and wet oxygen atmospheres. The oxide-ionic conductivity （σ） is affected by the doping level, and increases as follows： σ（x=0.02）σ（x=0.08）σ（x = 0.06）σ（x=0.04）. This order is consistent with that of the free volume of the crystal lattice. La2（Mo0.96V0.04）2O9-α has the highest oxide-ionic conductivity of 0.051 S·cm-1. The dependence of conductivity on oxygen partial pressure reveals that the samples are almost pure oxide-ionic conductors in the high oxygen partial pressure range whereas they exhibit mixed ionic and electronic conduction in the low oxygen partial pressure range.