The interaction of solid-solid phase transitions with convection in the Earth’s mantle involves, for univariant systems: (1) effects of latent heat and advection of ambient temperature on the position of the phase boundary and on its associated body force, and (2) the coupling of latent heat with the ordinary thermal expansivity of the material. For divariant systems, an effective thermal expan...

An in-situ Raman spectroscopic study was conducted to explore the pressure induced phase transformation of spinel-type ferrite ZnFe2O4. Results indicate that ferrite ZnFe2O4 initially transforms to an orthorhombic structure phase (CaFe2O4polymorph) at a pressure of 24.6 GPa. Such a phase transformation is complete at 34.2 GPa, and continuously remains stable to the peak pressure of 61.9 GPa. Th...

The surface and bulk compositions of the mixed metal oxide CoxNi1−xO have been compared over the entire range of stoichiometry 0 ≤ x ≤ 1. The materials, which were formed as polycrystalline solid solutions, were shown to be well-ordered and homogeneous in the bulk, but tend to deviate in their surface composition for x 0.6. Auger and X-ray photoelectron spectroscopy gave comparable results and ...

A sample having stoichiometry Li[Ti(1.5)Ni(0.5)]O(4) has been synthesized to obtain a spinel structure. The resulting crystalline powder revealed a multiphase nature with spinel as the minor phase. The main phase is a new trigonal phase having a = 5.05910 (1), c = 32.5371 (1) A. The structure has been solved by direct methods working on a three-dimensional set of intensities obtained from a pre...

Homogeneous lithium-rich layered-spinel 0.5Li2MnO3·0.5LiMn1/3Ni1/3Co1/3O2 microspheres (~1 μm) are successfully prepared by a solvothermal method and subsequent high-temperature calcinations process. The effects of temperature on the structure and performance of the as-prepared cathode material are systemically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission...

An equimolar mixtures of starting ZnO and Cr2O3 powders were mechanically activated by grinding using a planetary ball mill for various periods of time (40 to 320 minutes). Formation of nanocrystalline ZnCr2O4 as normal spinel structure at room temperature is detected in all samples after ball-milling. A detailed XRD structural analysis (lattice parameters, site occupancy, the average primary c...

TWO different spinels, analyses of which are given, occur in the layered ultramafic rocks at Dawros. Chrome spinel occurs both as gravity-stratified cumulates and as complex orbs, while an Al-rich spinel is both in rocks of the main Dawros magmatic sequence and in an association with an aluminous bronzite, which may originate by recrystallization. It is concluded that while the chrome spinel is...