Approach to rheology in the earth's crust based on the microstructure analysis

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This work has been done to elucidate rheology of the solid state earth's crust based on the microstructure analysis by means of mineralogical and crystallographic approaches. It is expected that some silicates have perovskite-type structure under high pressure and at high temperature in the earth's crust. Especially proton conduction of solid is considered to play an important role in rheology because water is believed to exist in the earth's crust.Some perovskite-type sintered oxides such as lanthanide element-doped SrCeO_3, BaCeO_3 and SrZrO_3 show the proton conductivity in hydrogen-containing atmosphere at high temperature. The chemical stability of SrZrO_3-based oxide is much better and 10 mol % Yb-doped SrZrO_3 oxide shows the highest proton conductivity among SrZrO_3-substituted zirconium with lanthanide elements.The powder samples of 5 and 10 mol % Yb-doped SrZrO_3 oxides been synthesized by solid state reaction using the corresponding oxides as starting materials. The materials synthesized have been studied by X-ray powder diffraction, thermogravimetric analysis(TGA), differential thermal analysis and X-ray absorption fine structure spectroscopy. The orthorhombic unit cell volume of 10 mol % one increases monotonously with increasing temperature but exhibits a bent between 500℃ and 600 ℃ which is about 300K lower than that of 5 mol % one. This bent of the unit cell volume is considered to be due to a loss of oxygen, which is consistent with the result of a weight loss in TGA observed in the same temperature range. In addition the displacements of oxide ions were observed were observed in the Fourier syntheses followed by a loss of oxygen at high temperature.In conclusion the oxygen behavior plays an important role in the conduction mechanism of proton in solids.