Iron-57 conversion-electron Mössbauer spectroscopic study of the initial stages of the oxidation of biotite

Abstract

The technique of ⁵⁷Fe conversion-electron Mössbauer spectroscopy is shown to be a viable method for the study of the early stages of solid-state reactions which start in regions close to solid surfaces. In particular. increases in the Fe³⁺ : Fe²⁺ ratio can be detected in a region confined to within 300 nm of the outer surfaces of a biotite flake which has been subjected to mild oxidation in air. These changes would have gone undetected if conventional transmission Mössbauer methods had been used alone. The reactions which occur in the surfaceregions of biotites during heat treatment in air are discussed.