Beta radiation effects in 137Cs-substituted pollucite

The effect of high-energy beta radiation on the long-range and local structure of 137Cs-substituted CsAlSi2O6 (pollucite) was studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques at the Cs K-edge. Analysis of the XRD pattern of pollucite with an absorbed dose of 1018 beta decays/g using Rietveld analysis indicates a 0.5–1% volume expansion of the tetrahedral structure as measured at 50 K and a minor displacement of the Cs cation toward the face of one of the six-membered rings. Analysis of the real-space pair-distribution function obtained from Fourier transformation of the diffraction pattern indicates significant correlated movement of the (Si,Al)–O pairs and large static disorder between Cs–O pairs. Analysis of the Cs K-edge XAS revealed substantial contributions from the Cs atomic X-ray absorption. This likely results from the exceedingly long Cs–O bond distances in the pollucite structure, which diminish the fine structure of the XAS oscillations, and the destructive interference of the backscattered photoelectron from static disorder between Cs–O pairs. In addition, a significant lengthening of the Cs–Cs interatomic distance was observed.