Synthesis of supersaturated type proton conducting oxides

由于掺入质子的目的是弥补受主掺杂引起的正电荷不足，因此受主掺杂的过饱和可以提高缺陷型质子导电氧化物的导电性。本文研究了α-Al_2O_3基氧化物体系中掺杂过饱和的三种方法：(1)冻结含有受主元素的第二相的高温平衡态；(2)强制还原深度掺杂到块体中的三价过渡元素；(3)低温烧结含有大量掺杂的非晶态氧化铝粉末。在第一种方法中，证实了可以获得具有较高质子电导率的材料，并且通过控制平衡状态的气氛来加速这一效应。在第二种方法中，发现掺杂元素的选择是实现质子电导率提高的关键。如果采用合适的烧结方法，则第三种方法是有效的。

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.