Superconductivity in LiTi₂O₄ Prepared by Hybrid Microwave Method

The well-known superconducting oxide LiTi₂O₄ has a structural phase transition from spinel to ramsdellite around 900°C. We have successfully obtained the superconducting spinel phase and the non-superconducting ramsdellite phase of LiTi₂O₄ using a hybrid microwave method. The samples are characterized by x-ray powder diffraction, scanning electron microscopy, and measurements of resistivity and magnetic susceptibility. The results show that the low-temperature spinel phase is a superconductor with T_c=13K, while the high-temperature ramsdellite phase is a semiconductor. By comparison between the crystal structures of the spinel and the ramsdellite phases, it is suggested that the geometrical frustration plays an important role in the superconductivity of the spinel LiTi₂O₄.