THE GROWTH AND CRYSTALLOGRAPHY OF BISMUTH TRI-IODIDE CRYSTALS GROWN BY VAPOR TRANSPORT

A single crystal of bismuth tri-iodide (BiI3) of dimensions 1.2 x 1.2 x 0.4 cm(3) has been grown by physical vapor transport. The lattice parameters of the hexagonal crystal and its polycrystalline powder precursor were measured by X-ray diffraction (XRD) and were in agreement, indicating that the vapor phase growth and sublimation purification processing at temperatures below 330 degrees C did not affect the stoichiometry. X-ray rocking measurements of the single crystal showed low angle boundaries of the order of 0.05 degrees. In tests as gamma radiation detectors, the vapor grown crystals were unsatisfactory, but observations suggest that better performance may be achievable with purer bismuth tri-iodide material.