Formation Behavior and High Electrical Conductivity of Metastable Lithium Iron Silicate Crystals in Rapid Quenching of Li 2 O – Fe 2 O 3 – SiO 2 Melts

The formation behavior of spinel‐type LiFeSiO 4 crystals in the quenching of melts in the Li 2 O – Fe 2 O 3 – SiO 2 system was examined. It was found that high quenching rates of 10 3  ~ 10 6  K/min are favorable for the formation of LiFeSiO 4 crystals. The rapid quenched samples showed high electrical conductivities of the order of 10 −2 –10 −4  S/cm at room temperature and low activation energy for conduction of 0.1–0.2 eV. Both valences of Fe 2+ and Fe 3+ were present in the melt‐quenched samples, and rapid‐quenched samples showed ferrimagnetism. It is proposed that the chemical composition of LiFeSiO 4 formed in the rapid quenching of melts would be spinel‐type Li 1 +  x Fe 3+ 1 −  x Fe 2+ x SiO 4 . Because the Li 1 +  x Fe 3+ 1 −  x Fe 2+ x SiO 4 crystalline phases are metastable, the rapid quenching technique is necessary for their synthesis. The effects of quenching rate and composition on the formation of spinel‐type LiFeSiO 4 and on the electrical conductivity of quenched samples were discussed.