A single crystal of bismuth tri-iodide @a3) of dimensions 1.2 X 1.2 X 0.4 cm3 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 0) and were in agreement, indicating that the vapor phase growth and sublimation purification processing at temperatures below 330°C did not si@icantly affect the stoichiometry. X-ray rocking measurements of the single crystal showed low angle boundaries of the order of 0.05". In tests as gamma radiation detectors, neither melt grown nor vapor grown crystals were satisfactory, but the vapor grown crystals were promising. Several observations suggest that better performance may be achievable with purer bismuth tri-iodide.

A single crystal of bismuth tri-iodide @a3) of dimensions 1.2 X 1.2 X 0.4 cm3 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 0) and were in agreement, indicating that the vapor phase growth and sublimation purification processing at temperatures below 330°C did not si@icantly affect the stoichiometry. X-ray rocking measurements of the single crystal showed low angle boundaries of the order of 0.05". In tests as gamma radiation detectors, neither melt grown nor vapor grown crystals were satisfactory, but the vapor grown crystals were promising. Several observations suggest that better performance may be achievable with purer bismuth tri-iodide.

A method to measure the amorphous calcium phosphate (ACP) content of plasma sprayed hydroxyapatite (HA) coatings is presented. The areas of the crystalline peaks and the broad amorphous "hump" in an X-ray diffraction scan of a mixture of crystalline and amorphous HA can be fitted using conventional nonlinear least-squares methods. The weight fraction of the amorphous component in a mixture of unknown proportions is obtained from the measured hump fraction using a linear expression requiring a single calibration constant. This calibration constant may be determined by applying the same sample preparation, X-ray measurement, and least-squares fitting methods to a single standard of known (weighed) proportions as used to measure the unknown(s). Application of this method to a set of 12 samples yields an "index of crystallinity" for plasma sprayed HA coatings with an estimated standard deviation of 1 wt % ACP across the entire compositional range.

Pyrite single-crystal cubes were cut, polished. and x-rayed to produce orientations of (100), (110), (111), and (112). These crystallographically developed surfaces then were prepared to expose an area of 1 cm(2), and the remainder of the crystal was coated with an acid-resistant silicone cement. Crystals with representative orientations then were leached in ferric sulfate solutions adjusted to a pH of 2.3 with H(2)SO(4) containing up to 6 x 10(3) ppm of Fe(3+) at 30 and 55 degrees C. Leaching was also conducted in acid-bacterial lixiviants containing Thiobacillus ferrooxidans at 30 degrees C and a thermophilic microorganism at 55 degrees C. Surface corrosion and pitting associated with pyrite leaching were examined by scanning electron microscopy. Pyrite leaching in ferric sulfate solutions was observed to be different when compared to acid-bacterial leaching. Ferric sulfate leaching required nearly 2 x 10(3) ppm of Fe(3+) at 30 degrees C while acid-bacterial leaching at 30 degrees C occurred without additions of Fe(3+), and values of Fe(3+) never exceeded 10(2) ppm. Because of precipitate formation, an accurate assessment of the role of crystallographic orientation on the leaching of pyrite is difficult.

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