Incongruent, time-dependent chemical vapour transport in multi-component systems: A case study in Cr–Ge–Si

Single crystals of various compounds in the ternary system Cr–Ge–Si were grown by chemical vapour transport (CVT) with iodine in a temperature gradient from 800 to 1000 °C. The transport of the solid solution phases Cr(Ge,Si)3 and Cr5(Ge,Si)3 was found to be strongly incongruent and time-dependent. While individual sink crystals are homogeneous and do not show any composition gradient (core–shell structure), the sink a whole is strongly inhomogeneous showing a uniform distribution crystal compositions over a wide composition range. Possible explanations for the observed transport mechanism and implications for synthetic use of incongruent transport systems are discussed. An isothermal section of the ternary phase diagram at 800 °C is given.

Single crystals of solid solution phases with individual compositions distributed over a wide range can be grown by a single CVT experiment.Figure optionsDownload as PowerPoint slide