Vapor species evolved from Li_2TiO_3 heated at high temperature under various conditions

摘要

Li_2TiO_3 is one of the most promising candidates among proposed solid breeder materials in fusion reactors because of its chemical satiability. Addition of H_2 or H_2O to inert sweep gas has been proposed for enhancing the release of bred tritium from breeder material in fusion reactors. However, its vaporization characteristic has not been well established. Application of an atmosphere-controlled high-temperature mass spectrometer has provided the vapor pressure data of Li-compounds evolved from Li_2TiO_3, under individual conditions of vacuum, D_2, D_2O and O_2 atmospheres. The observed characteristics of vapor species evolved from Li_2TiO_3 under these conditions are presented here. The sum of the partial pressures of Li-containing species was figured out. The highest pressure was obtained in D_2 followed by D_2O and then, in vacuum, with the lowest being in O_2. Furthermore, the temperature dependence of Li vapor pressure indicated that Li-containing species appeared above 1273 K in vacuum and O_2 atmosphere, and above 973 K in D_2 or D_2O atmospheres. After the vapor pressure measurement in D_2 atmosphere, the color of the sample changed from white to dark blue. This change of color with the oxygen content decreased, suggested change from Ti~(4+) to Ti~(3+) in reduction atmosphere.