Thermal processing and crystallization of amorphous Mg-Ca silicates

Abstract

The structural evolution of sol-gel-produced amorphous Mg(x)Ca(1-x)SiO3 silicates is investigated. Mid-IR Fourier transform infrared spectroscopy and synchrotron X-ray diffraction are used to confirm the amorphous nature of the as-prepared silicates, while subsequent in situ synchrotron X-ray powder diffraction measurements are used to study the evolution of crystalline mineral phases as a function of annealing temperature. Multiple silicate phases, including diopside, enstatite, forsterite, and SiO2, are identified, while Rietveld (i.e., structure) refinement of the diffraction data is used to quantify phase change relationships. Investigated as possible analogs for the refractory dust grain materials likely to have been present in the early solar nebula, the likely relevance of these investigations to the observed silicate compositions of chondritic meteorites and cometary bodies and the processing of their precursor materials is discussed. © The Meteoritical Society, 2013.