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 × 2.3 mm × 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 ∼154 K and ∼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 T2. Therefore, our results apparently do not support the Fermi liquid model proposed in the literature.