Reactions of bismuth in sulfur/iodine flux mixtures produce BiSI and Bi19I3S27 as needle-shaped crystals. Variation of the iodine content of the flux allows for selectivity over the product; as a result, we can synthesize the metastable Bi19I3S27 in high yield. Both of these phases are semiconductors. Their band gaps can be tailored by addition of antimony into the synthesis mixture. Bi1-xSbxSI forms over the entire stoichiometric range, but Bi19-xSbxI3S27 can only incorporate a limited amount of Sb (up to x = 5). The unit cell parameters of Bi1-xSbxSI decrease as expected as the antimony content increases. However, the band gap does not follow a Vegard's law dependence on Sb substitution. Raman spectroscopy of Bi1-xSbxSI (x = 0.33 and 0.5) crystals show vibrational modes similar to both parent compounds, indicating that segregation and nanostructuring may be occuring instead of solid solution formation.

Synthesis of bismuth sulfide iodides in sulfur/iodine flux mixtures

251st National Meeting (2016)

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