Amorphous silicate nanoparticles with controlled Fe-Mg pyroxene compositions

• Amorphous nanoparticles produced from a sol-gel dried under high vacuum
• Controlled FeMg pyroxene compositions
• Fe fully incorporated into silicate network
• Structural domains 10 × smaller than particle size

The production of amorphous pyroxene nanoparticles (~ 20 nm) with controlled Fe-Mg content is described. Homogenous particle compositions closely matching required target stoichiometries are obtained by drying a precursor gel under high vacuum conditions. The silicate nature of the particles is characterised using TEM, synchrotron radiation and FTIR. No oxide phase separation occurs, even at high Fe concentration. Structural domains exist within the nanoparticles that are typically ten times smaller than the physical particle size consistent with either a core-shell, or, random network with multiple embedded domains, particle structure. Thermal annealing below the crystallisation temperature allows the ordered domain size to be further reduced by a factor of ~ 2.