Estimation of free energies for Li8SiO6 and Li4SiO4 and calculation of the phase diagram of the Li-Si-O system

Based on new experimental results in the literature for the Li2O-SiO2 system, the free energies of Li8SiO6 and Li4SiO4 in the temperature range 700 to 1100 K are estimated to be G0(Li4SiO4) = -1.174x10-4T2-0.1607T-2296 kJ/mol, G0(Li8SiO6) = -2.017x10-4T2-0.2332T-3480 kJ/mol. The Li-Si system is presented including the new intermetallic compounds Li22Si5, Li13Si4, Li7Si3 and Li12Si7 as described in the literature. The phase field distribution of the Li-Si-O system is calculated and ternary isothermal sections as well as Ellingham diagrams are presented and discussed with respect to the stability of Li-silicates in liquid Li. The use of Li8SiO6 as a solid breeder material in fusion reactors seems to be unlikely since already small variations of the Li, Si or O2 pressure make the compound chemically instable. (orig.)