Large Size Single Crystal Growth of Ti4O7 by the Floating-Zone Method

We report the growth of large size Ti4O7 single crystals by the floating-zone method using an infrared image furnace. By employing a high rotation rate of the seed rod, we improved the temperature gradient at the solid-liquid interface, thereby suppressing the decomposition of Ti4O7 at high temperature. By systematically studying the influence of growth parameters on crystal quality, we found that pure argon atmosphere is a prerequisite for getting a pure Ti4O7 phase and that a moderate rotation rate of the seed rod is a critical element in obtaining high crystal quality. The X-ray rocking scan confirmed the quality of the grown single crystal with dimensions of 2.7 mm X 2.3 mm X 1.7 mm, which was further characterized by electrical resistivity measurements. With decreasing temperature, the electric resistances of the Ti4O7 single crystal along a, b, and c axes all have two abrupt drops at similar to 154 K and similar to 110 K but show significant anisotropy. Moreover, it is noteworthy that the resistivity of the Ti4O7 single crystal in the high-temperature (HT) phase (T > 154 K) exhibits different behavior along different axes, exhibiting semiconducting behavior along the b axis but unusual metallic behavior along the a and c axes, in which the resistivity is proportional to T instead of T-2. Therefore, our results apparently do not support the Fermi liquid model proposed in the literature.