Electrical Characterization of Phase Changes in Lithium Titanate

Phase changes in the quenched R phase (ramsdellite structure Li2Ti3O7) synthesized by the melt-quenching method were evaluated in terms of the electrical property change. The electrical resistivity and dielectric constant varied in accordance with the thermal expansion behavior, indicating their effectiveness for studying the phase changes. The effect of adsorbed water on the electrical properties of the R phase was observed in the temperature range of 100 to 400°C. A sharp increase in resistance was observed above 550°C, which did not coincide with the thermal expansion behavior. This phenomenon indicated the decrease in Liion conductivity taking place prior to the phase change from R to H phase. The single phase spinel structure Li4Ti5O12 (S phase) was synthesized, and electrical measurements and crystallographic analyses were also conducted. Powder X-ray diffraction of the S phase gave rise to results different from those of Deschanvres et al. Its lattice constant and linear thermal expansion coefficient were precisely determined to be α=0.83588 (2) nm and α=1.49×10-5K-1, respectively. The S phase was confirmed to be an electric insulator.