SOL-GEL SYNTHESIS OF TARGETED COMPOSITION NANOSCALE OLIVINE

Olivine, (Mg,Fe)₂SiO₄, is one of the most prominent rock forming minerals within our solar system. Olivine is an orthorhombic orthosilicate that varies in composition from forsterite (Mg₂SiO₄ – Fo100) to fayalite (Fe₂SiO₄ – Fo00), and has a variety of research and industrial applications. Many intermediate compositions, including those more commonly found on extraterrestrial bodies, are difficult to obtain on Earth, prompting a need for a synthetic source of intermediate compositions for experimentation and other uses. By combining previously established sol-gel synthesis methods for producing synthetic forsterite (Anovitz et al. 2017) and fayalite (DeAngelis et al. 2012), a new hybrid method was developed to synthesize targeted intermediate composition olivine. Using this new method, targeted olivine compositions matching Fo100 (100% Mg), Fo82 (82% Mg), Fo53 (53% Mg), Fo43 (43% Mg), Fo31 (31% Mg), Fo21 (21% Mg), and Fo00 (0% Mg) have been produced. Analysis included X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET surface area analysis. XRD analysis shows predictable pattern shifts in composition along the solid solution series, with pattern software assisted analysis estimating the crystallite sizes ranging from < 40 nm - 147 nm. All successfully synthesized samples have ranged within 5% of the target elemental composition, and surface area analysis indicates surface areas up to ~80 m²/g. Though it can be challenging to obtain specific intermediate composition with any synthesis method, careful and accurate measurement of starting materials, along with maintaining the proper reducing environment during synthesis, has resulted in achieving the desired target composition, while maintaining nanoparticle size, using this method.