Development of super high temperature-type proton conductor based on alpha alumina.

首先，以α-氧化铝单晶为原料，研究了掺氢的最佳掺杂剂。通过对羟基伸缩振动红外吸收光谱的测量，发现镁是镁、镍、钴、钛中最有效的掺杂剂。为了改善热应力引起的晶体生长成品率低的问题，研究了添加Cr、Y、B、Sm、Nd、La、Ce作为二次掺杂的方法。用掺镁样品研究了掺氢在α-Al_2O_3晶体结构中的位置。考察了几组入射光束和晶面的偏振角对OH伸缩振动吸收的影响。测量结果与理论计算结果的比较表明，氢位于刚玉结构中形成氢键的氧八面体边缘的0-0键之间。AM…此外，在四个不同间距的0-0键中，一个间距为272 pm的键更有利于氢的定位。掺钛的α-铝也有相同的趋势。研究了掺镁单晶样品的电导率的H/D同位素效应。在低氧电位区，质子是最主要的载流子。在电导中也观察到了各向异性。当电场方向垂直于c轴时，电导率高于平行电场方向，这可以用氢原子在O-O键之间的优先位置来解释。由于镁是最合适的掺杂剂，所以用市售的主要杂质为镁的多晶氧化铝管进行了电化学性能的研究。在不同的氢气和氧势梯度下，测量了以这些管子为电解液的氢浓差电池的电动势。根据晶体缺陷模型对这些值进行了理论分析，导出了电池电动势与电极电位差之间的关系式。此外，还研究了镁铝尖晶石的电化学性质，以了解第二相对质子导电性能的影响。证实了氢以质子形式存在于镁铝尖晶石中，并具有可移动性。然而，镁离子的电导率要高得多，质子对电导率的贡献可以忽略不计。较少

Firstly, the most appropriate dopant for incorporation of hydrogen was studied using single crystal of alpha alumina. With the measurements of IR absorption of OH stretching vibration, the magnesium is found most effective dopant among Mg,Ni,Co, and Ti. In order to improve the low yield of crystal growth due to the thermal stress, the additions of Cr,Y,B,Sm,Nd,La,Ce as the second dopant were examined. However, the any explicit improvements were not obtained.The location of the incorporated hydrogen in the crystal structure of alpha-alumina was investigated with the Mg doped samples. The polarization angle dependency of the absorption of OH stretching vibration was examined for several sets of the directions of the incident beam and crystal faces. The comparison between the measurement and the theoretically calculated results showed that hydrogen is located between one of the 0-0 bond constituting the edges of oxygen octahedron in the corundum structure with making the hydrogen bond. Am … More ong the four 0-0 bonds of different spacing, one whose spacing is 272 pm is found preferred for hydrogen location. The same tendency was observed for Ti doped alpha-alumina.The H/D isotope effect of electrical conductivity was examined for Mg doped single crystal samples. The proton was confirmed to be the most dominant charge carrier in the low oxygen potentials region. The anisotropy was observed also in the electrical conduction. The conductivity was higher when the direction of the electric field is perpendicular to c-axis than pararell, which was reasonably explained by the preference of hydrogen location among the O-O bonds.As the Mg was found to be the most appropriate dopant, the electrochemical properties were studied with the commercially supplied polycrystalline- alumina tube whose main impurities were magnesium. The emf of the hydrogen concentration cells using these tubes as the electrolyte were measured for various hydrogen and oxygen potential gradients. These values were analyzed theoretically based on the model of the crystal defects and the equation between the emf of the cell and the potentials difference on the electrodes was derived. The parameter appeared in the equation was determined as a function of the temperature.The electrochemical properties of magnesium-aluminate spinel which is almost always the co-existing phase of Mg-doped polycrystalline -alumina were also studied to know the effect of second phase on the properties of the proton conduction. It was confirmed that hydrogen might be incorporated into magnesium-aluminate spinel as proton and that the it was movable. However, the conductivity due to magnesium ion was found far higher and the contribution of proton to the electrical conductivity could be ignored. Less