An Expanded EXAFS Model of Mn, Zn, and Fe Spinel Nanoparticles

The structure of Mn, Zn, Fe spinel nanoparticles, obtained by coprecipitation from reversed microemulsions, deviates progressively with the diminishing particle size from the bulk spinel structure. The deviations can in principle be extracted from EXAFS spectra of constituent metals, but with additional parameters to describe the deviations, the problem may not remain statistically well-posed. With a simultaneous analysis of the spectra, enabled by the recently available IFEFFIT code, the well-posedness is regained, and several types of deviations, introduced by nanoscopic size or by varied stoichiometry of oxide mixtures can be quantified: the changes in site occupations, the distortion of the lattice and the fraction of vacancies.