Hydrogen and deuterium diffusion in non-stoichiometric spinel
Hydrogen and deuterium diffusion in non-stoichiometric spinel
复制标题
DOI：
10.1080/08957959.2017.1353091
复制
发表时间：
2017-01-01
影响因子：
2
通讯作者：
Kohn, Simon C.
中科院分区：
文献类型：
--
作者：
Bromiley, Geoffrey D.;Brooke, Jennifer;Kohn, Simon C.
高压/高温退火实验被用来确定扩散系数的H+和D+在非化学计量尖晶石，低压模拟名义上无水矿物在地球的地幔。数据符合以下Arkenius定律：扩散率（m（2）/s）= 4 +/- 1 x 10（-12）exp（-54 +/- 2 kJ mol（-1）/RT）。在低温下，H+和D+在非化学计量尖晶石中的扩散通过O空位的通量而电荷平衡，红外数据与非化学计量尖晶石中的八面体和四面体O-O边缘的质子化一致，并且由于Mg-Al混合和/或结构上并入的H+与阳离子空位的耦合而产生额外的精细结构。在O-H吸收带的精细结构的变化的情况下，表明H+可以成为局部耦合和不耦合到其他缺陷在体扩散。因此，在尖晶石族矿物的质子电导率，所产生的非耦合H+的更快的流量，只能从H+迁移率数据计算，如果缺陷耦合的程度受到限制。
High pressure/temperature annealing experiments are used to determine diffusivities of H+ and D+ in non-stoichiometric spinel, a low-pressure analogue for nominally anhydrous minerals in Earth's mantle. Data are fitted to the following Arrhenius law: Diffusivity (m(2)/s) = 4 +/- 1 x 10(-12) exp(-54 +/- 2 kJ mol(-1)/RT). At low temperatures, H+ and D+ diffusion in non-stoichiometric spinel is charge balanced by flux of O vacancies, with infrared data consistent with protonation of both octahedral and tetrahedral O-O edges in non-stoichiometric spinel, and additional fine structure due to Mg-Al mixing and/or coupling of structurally incorporated H+ with cation vacancies. Absence of changes in the fine structure of O-H absorption bands indicates that H+ can become locally coupled and uncoupled to other defects during bulk diffusion. As such, proton conductivity in spinel group minerals, arising from faster flux of uncoupled H+, can only be calculated from H+ mobility data if the extent of defect coupling is constrained.