Energetics of Cs in Sigma3 grain boundary of 3C-SiC

TL;DR

This study uses density functional theory to analyze cesium defect energetics at Sigma3 grain boundaries in 3C-SiC, revealing enhanced stability at boundaries and implications for controlling cesium release in nuclear fuel applications.

Contribution

It provides new insights into cesium defect stability at grain boundaries in 3C-SiC, suggesting grain-boundary-engineering as a method to control cesium release.

Findings

Cesium is more stable at Sigma3 grain boundaries than in bulk SiC.

Formation energies of Cs at grain boundaries are significantly lower (7-17 eV) than in bulk.

Cs has lower formation energies than Ag at the grain boundaries, opposite to bulk behavior.

Abstract

Energetics of Cs defects at Sigma3 grain boundaries of 3C-SiC has been studied using density functional theory to understand the role of the grain boundaries in Cs diffusion and its eventual release from the tristructural isotropic fuel particles (TRISO). Cs is shown to be much more stable at the Sigma3 grain boundary than in bulk of SiC with a significant decrease (7-17eV) in the formation energies at the grain boundaries than in bulk. It is found to have even lower formation energies than those of Ag at the Sigma3 grain boundaries, while this trend was opposite in the bulk SiC as demonstrate previously from similar density functional theory calculations. Based on these results, a possible route to control Cs release from SiC layer via grain-boundary-engineering is suggested.