Synthesis of supersaturated type proton conducting oxides

可以预期通过受体掺杂剂的过饱和来增强缺陷型质子传导氧化物的导电性，因为质子被引入以补偿由受体掺杂引起的正电荷的缺乏。在本研究中，对α氧化铝基氧化物系统的掺杂剂过饱和进行了以下三种方法的研究：（1）与含有受主元素的第二相的高温平衡状态的冻结，（2）深度掺杂到体中的三价过渡元素的强制还原，以及（3）低温反应合成的含有大量掺杂剂的无定形氧化铝粉末的低温烧结。在第一种方法中，证实了可以获得具有更高质子传导率的材料，并且通过将气氛控制在平衡状态来加速该效果。在第二种方法中，发现掺杂剂元素的选择对于实现质子传导率的增加是关键的。第三种方法是有效的，如果采用适当的烧结方法。

An enhancement of the conductivity of the defect-type proton conducting oxide by the super saturation of acceptor dopant can be expected because the proton is incorporated in order to compensate the lack of positive charge induced by the acceptor doping. In the present research, the following three methods of super saturation of dopant were examined to the alpha alumina-base oxide system : (1) freezing of the high-temperature equilibrium state with the second phase containing the acceptor element, (2) forced reduction of trivalent transition element deeply doped into the bulk, and (3) low-temperature sintering of amorphous alumina powder containing a large amount of dopant synthesized at low temperature reaction. In the first method, it was confirmed that the material with the higher proton conductivity could be obtained and that the effect was accelerated by controlling the atmosphere at the equilibration state. In the second method, it was found that the selection of the dopant element is critical to realize the increase of the proton conductivity. The third method was ascertained effective if the proper method of sintering was employed.