Diffusion of proton in alumina-rich nonstoichiometric magnesium aluminate spinel

Abstract

The phenomenon of the diffusion of proton and deuteron in a single crystal of magnesium aluminate spinel was studied by infrared absorption. The chemical diffusion coefficient of proton was determined by the relaxation time of the absorption intensity upon the substitution of deuteron with proton. The temperature dependence of the chemical diffusion coefficient of proton for Mg 1Àx Al 2 O 4Àd x ¼ 0:34 ð Þ was expressed as e D ¼ 0:16 exp À210 Â 10 3 Jmol À1 K À1 À Á À RT Þcm 2 s. The chemical diffusion coefficient of proton was found to be independent of the composition of spinel and of the atmosphere.

Diffusion in Oxides

“…The activation enthalpy for electrical conduction was found to be 248 kJ/mol, within the range of values for cation diffusion discussed above. Okuyama et al (2009) examined the exchange of deuterons and protons in experiments in which a plate of spinel was pre-equilibrated in either an H 2 O or D 2 O atmosphere, and then annealed in an atmosphere containing the other isotope, at the same water vapor pressure. Their results are similar to those of Fukatsu et al (2002) for bulk chemical diffusion of water, and in addition demonstrate that the H/D interdiffusion coefficient is independent of the partial pressure of water vapor.…”