Tritium release and defect evolution in neutron-irradiated Li 2 Pb x Ti 1-x O 3 ceramic pebbles

Achieving tritium self-sufficiency remains a key challenge for future fusion reactors, creating a strong need for breeder materials with efficient tritium release. In this study, neutron-irradiated Li2PbxTi1-xO3 (x=0, 0.05, and 0.1) ceramic pebbles were investigated by tritium thermal desorption spectroscopy (T-TDS) and electron spin resonance (ESR). Tritium release was examined at different heating rates and under isothermal conditions, and the corresponding kinetic parameters were determined. All samples exhibited a single tritium desorption peak that shifted to higher temperatures with increasing heating rate, confirming a thermally activated release process. Pb introduction broadened the desorption peak and lowered the apparent activation energy for tritium release. Under isothermal heating, the tritium diffusion activation energy (Ed) and pre-exponential factor (D0) increased simultaneously, following the compensation effect and suggesting multiple migration pathways. ESR isochronal and isothermal annealing showed that irradiation-defect annihilation occurs in two stages: a fast stage associated with electron migration and a slower stage governed by oxygen diffusion. The defect-annihilation range overlaps strongly with the main tritium-release range, indicating that tritium release is jointly controlled by diffusion and defect evolution. Pb addition accelerates defect annihilation and broadens the defect-recovery temperature range, thereby regulating tritium migration and release through changes in defect stability.