The effect of annealing at 1500 deg C on migration and release of ion implanted silver in CVD silicon carbide

The transport of silver in CVD (3-SiC has been studied using ion implantation. Silver ions were implanted in (3-SiC using the ATLAS accelerator facility at the Argonne National Laboratory. Ion beams with energies of 93 and 161 MeV were used to achieve deposition with peak concentrations of approximately 26 wt% at depths of approximately 9 and 13 urn, respectively. As-implanted samples were then annealed at 1500 deg C for 210 or 480 h. XPS, SEM, TEM, STEM, and optical methods were used to analyze the material before and after annealing. Silver concentration profiles were determined using XPS before and after annealing. STEM and SEM equipped with quantitative chemical analysis capability were used to more fully characterize the location and morphology of the silver before and after annealing. The results show that, within the uncertainty of measurement techniques, there is no silver migration, via either inter- or intra-granular paths, for the times and temperature studied. Additionally, the silver was observed to phase separate within the SiC after annealing. The results of this work do not support the long held assumption that silver release from CVD SiC, used for gas-reactor coated particle fuel, is dominated by grain boundary diffusion.