Formation of multicomponent alloy particles in doped ceria under I2+ ion irradiation and thermal annealing

•Work provides new understanding of the early stages of alloy particle formation in nuclear fuel in the presence of fission gas.•Doped CeO2 was used as a surrogate for UO2 along with implantation with fission gas to avoid the challenge of handling radioactive material.•The combined effects of heavy recoil damage and elevated temperature led to multicomponent precipitate formation•Iodine segregated to extended defects.•Re, the surrogate for 99Tc, was found in precipitates formed at 900 °C