Lithium Vapor Chemistry of Hyper-Stoichiometric Lithium Metatitanate Li_2.12(2)TiO_3+y

Abstract

Developing a better ceramic breeder (Li-containing oxide) is a key challenge for realizing fuel-self-sufficient fusion reactors. Ceramic breeder pebbles of hyper-stoichiometric lithium metatitanate, Li2+xTiO3+y (Li/Ti > 2), have been developed for a demonstration fusion reactor as high Li density enhances fuel tritium production. Previous studies have reported that Li loss by vaporization at high temperatures was largely enhanced by the increase in Li/Ti ratio and environmental moisture concentration. Minimizing the Li loss is a key issue for sufficient tritium breeding and reduced corrosion of structural steel. However, a suitable environmental parameter for hyper-stoichiometric Li2+xTiO3+y pebbles has not yet been determined because of unavailability of thermodynamic data. Herein, a solid/gas equilibria for Li2.12(2)TiO3+y was investigated by measuring vapor pressures using atmosphere controllable Knudsen cell high temperature mass spectrometry. The enhanced thermodynamic activities of Li and Li2O in Li2.12(2)TiO3+y in comparison with those in stoichiometric Li2TiO3 were obtained as functions of temperature and oxygen concentration. The equilibrium constants were used to achieve the optimum moisture concentration that can suppress the vapor reactions in a cylindrical breeding zone with inhomogeneous temperature distribution.Li 2.12(2) TiO 3+y L i ( g ) L i O H ( g )

Hydrogen permeation from F82H wall of ceramic breeder pebble bed: The effect of surface corrosion

“…This indicates that gas release from the LTZO pebbles during the initial heating period resulted in the formation of oxide layers on the F82H samples, which readily suppressed hydrogen permeation. In this moisture range, the gas phase of LiOH is a dominant corrosive gas, based on the previous thermochemical analysis of Li2.12(2)TiO3+y [37]. The ion current after the initial heating gradually decreased with the growth of the oxide layer on the F82H samples.…”

Characterization of cation disorder and oxygen vacancies in Li‐rich Li2TiO3

“…To solve this issue, hyperstoichiometric lithium metatitanate Li 2+ x TiO 3+ y (Li/Ti > 2) has been developed for years as an advanced ceramic breeder for its higher stability in the hydrogen atmosphere and enhanced tritium production. The Li‐rich Li 2 TiO 3 is confirmed to have a resistance to the reduction of Ti (Ti 4+ → Ti 3+ ), which forms oxygen defects and a higher partial pressure of Li‐containing species 14,15 …”

“…The Li-rich Li 2 TiO 3 is confirmed to have a resistance to the reduction of Ti (Ti 4+ → Ti 3+ ), which forms oxygen defects and a higher partial pressure of Li-containing species. 14,15 The defect chemistry in Li-rich Li 2 TiO 3 is still unclear, and it is important to reveal the structure of Li-rich Li 2 TiO 3 that helps to understand the behavior of produced tritium and estimate irradiation defects. Many efforts have been devoted to investigating the structure of Li-rich Li 2 TiO 3 .…”

Fabrication of submicron Li‐rich Li2(Ti,Zr)O3 solid solution ceramics with sluggish grain growth rate

“…[14][15][16][17][18][19] As Li 2 TiO 3 has a broad stoichiometric range with Li/Ti ratios varying from 1.88 to 2.25, 20 Hoshino et al developed the singlephase Li-doped Li 2 TiO 3 as an advanced tritium breeder and found that not only the Li density is increased but also the chemical stability under operating conditions is enhanced. [21][22][23][24] Based on this, to control the grain growth during sintering, the possibility of a solid solution for the Li 2 O-TiO 2 -ZrO 2 system is surveyed by a conventional solid-state reaction, in which Li 2 TiO 3 and Li 2 ZrO 3 were first synthesized and then reacted to form the solid solution. 25 However, this method requires multiple heating cycles at high temperatures, which easily yields the problems, such as high-energy consumption, poor sinterability, Li 2 O sublimation, and uncontrolled grain growth.…”