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Li2TiO3 is one of the most promising candidates for solid breeder materials. However, defects introduced in Li2TiO3 will affect tritium release. In the present study, vacuum-annealing defects in Li2TiO3 were investigated by means of electron spin resonance (ESR). The defects of E-centers were found to be introduced by vacuum-annealing in Li2TiO3. The color of Li2TiO3 samples becomes dark grey after annealing in vacuum. This color change suggests the change from Ti4+ to Ti3+ due to decrease in the oxygen content. And the color was observed to recover to initial color, white again after annealing in air. The concentration of vacuum-annealing defects reaches almost a constant when the pressure is lower than 10 Pa. The defect concentration increases as annealing temperature goes up and then decreases when the temperature reaches to a certain value. The amount of vacuum-annealing defects goes down and the color of Li2TiO3 samples recovers to white gradually when vacuum-annealing samples annealed in air at different temperatures. There are no defects and color change while Li2TiO3 samples anneal in air first and then transfer to vacuum tube rapidly for vacuum-annealing. More defects were introduced in Li2TiO3 samples immersed in water for 6 hours. This elucidates that the defects produced by vacuum-annealing are attributed to the reduction of water adsorbed in Li2TiO3. Mass of Li2TiO3 was found to vary after the change of the atmosphere from nitrogen to air investigated by thermogravimetry. X-ray diffraction (XRD) results indicate that there are no modifications on Li2TiO3 crystal phases.
The authors acknowledge School of Materials Science and Engineering in University of Science and Technology Beijing for providing the experimental samples. This work supported by the National Natural Science Foundation of China under contract No. 11605230.
| Eligible for student paper award? | No |
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