Single-crystal growth of sulphospinel CuIr2S4 from Bi solution

Single crystals of a sulphospinel CuIr₂S₄ have been grown from bismuth solution by a slow cooling method for the first time. The grown crystals have a maximum edge of about 1 mm in size and a mirror-like shining surface. Optimum growth conditions are fairly strict. The specific weight of starting materials for the crystal growth is found to be 0.30 g of CuIr₂S₄ and 10.0 g of Bi in order to obtain good quality crystals. The starting and finishing temperatures for the slow cooling step in the temperature control are 1000 and 500°C. The pertinent cooling rate is 2°C/h. Since the volume of bismuth itself expands in the transition from liquid phase to solid phase, a simple method of separation of the grown crystals from the liquid solution will be proposed for avoiding the mechanical damages to the grown crystals. The single crystals have the normal-spinel structure of the lattice constant a=9.849 Å at room temperature. A step-like anomaly in the susceptibility of the single crystals, corresponding to the metal–insulator transition in the resistivity, occurs much sharply than in the powder specimen.