Local Structural Information of Mullite Obtained from Diffuse X-ray Scattering

Abstract

A full reciprocal space volume of diffuse scattering data from a single crystal of the mineral mullite, Al2(Al2+2x,Si2-2x)O10-x, x = 0·4, has been collected. These data were analysed using least-squares techniques by writing an equation for the diffuse scattering which involves only the local order between vacancies on specific oxygen sites in the material. The effect of the large, but predictable, cation shifts on the diffuse intensity was taken account of in the coefficients to the oxygen vacancy short-range order intensities. This analysis shows that in addition to the absence of defects separated by the vectors 1/2〈110〉 and [110] (which results from the simplifying assumptions that were made), there is also a strong tendency to avoid defects separated by 〈001〉 and a moderately strong tendency to avoid pairs of defects separated by 〈003〉, 〈011〉, [1-10] and 1/2〈3 2〉. The most common interdefect vectors found were 1/2〈310〉, 〈101〉, 1/2〈112〉, 〈012〉, 1/2〈130〉, 1/2〈132〉 and 〈022〉. Show more