Deformation of polycrystalline MgO at pressures of the lower mantle

Abstract

[1] Room temperature investigations on the shear strength, elastic moduli, elastic anisotropy, and deformation mechanisms of MgO (periclase) are performed in situ up to pressures of 47 GPa using radial X-ray diffraction and the diamond anvil cell. The calculated elastic moduli are in agreement with previous Brillouin spectroscopy studies. The uniaxial stress component in the polycrystalline MgO sample is found to increase rapidly to 8.5(±1) GPa at a pressure of 10(±1) GPa in all experiments. Under axial compression, a strong cube texture develops which was recorded in situ. It is probable that the preferred orientation of MgO is due to deformation by slip. A comparison between the experimental textures and results from polycrystal plasticity suggest that the {110}h1 " 10i is the only significantly active slip system under very high confining pressure at room temperature. These data demonstrate the feasibility of analyzing elastic moduli, shear strength, and deformation mechanisms under pressures relevant for the Earth's lower mantle. Implications for the anisotropy and rheology of the lower mantle are discussed.

Diamond anvil cell deformation of CaSiO3 perovskite up to 49GPa

“…In order to interpret our experimental textures we use the viscoplas-A c c e p t e d M a n u s c r i p t tic self-consistent polycrystal plasticity model (Lebensohn and Tomé, 1993) to simulate texture evolution in cubic perovskite polycrystal deformed by slip under axial compression. The experimental texture pattern of CaSiO 3 perovskite in axial compression is similar to textures obtained for MgO (Merkel et al, 2002), a cubic minerals with low temperature slip systems of {110}<110>. This is the same slip system that has been proposed for cubic perovskites at low temperature (Poirier et al, 1989) and observed at high temperature in CaTiO 3 (Besson et al, 1996) and SrTiO 3 (Wang et al, 1993).…”

“…Solid lines are guide to eyes through the data. M a n u s c r i p t (Merkel et al, 2003), open triangles results for MgO (Merkel et al, 2002), grey diamonds results for olivine (Uchida et al, 1996), open diamonds results for ringwoodite (Kavner and Duffy, 2001), and open circles results for SiO 2 (Shieh et al, 2002). Lines are guides to the eyes through the experimental data.…”

“…The mechanical properties of high pressure minerals can be studied using radial x-ray diffraction in the diamond anvil cell (DAC) (Merkel et al, 2002). In those experiments, a polycrystalline sample is confined under non-hydrostatic stress in a DAC.…”

Hard X-ray studies of stress-induced phase transformations of superelastic NiTi shape memory alloys under uniaxial load

“…Local background subtraction and polarization correction is also applied to the measured intensities [11]. Diffraction intensities were extracted with FIT2D into a multicolumn ASCII spread sheet [12], where each column corresponds to an intensity distribution along the azimuth for a particular 2θ value. The peak positions were identified from full profile analysis using the GSAS refinement code [13] and intensity versus azimuth data for particular reflections were extracted.…”

Experimental method for in situ determination of material textures at simultaneous high pressure and high temperature by means of radial diffraction in the diamond anvil cell

“…1͒. Most of these experiments are only possible because of the use of x-ray transparent gaskets, consisting of amorphous B inserts [6][7][8][9] or Be 3,4 that allow the collection of x-ray diffraction data from samples perpendicular to the loading axis. Radial diffraction has also been used to study texture and crystallographic preferred orientations ͑CPOs͒ in plastically deformed materials 10 by measuring intensity variations along the Debye rings.…”