In Situ Neutron Diffraction Studies of the Metal Flux Growth of Ba/Yb/Mg/Si Intermetallics.

The Ba/Yb/Mg/Si intermetallic system is extremely complex, with four competing structurally related compounds forming from reactions of barium, ytterbium, and silicon in magnesium-rich Mg/Al flux. In addition to the previously reported BaYbMgSi, BaYbMgSi, and BaYbMgSi, a new compound has been found. BaYbMgSi crystallizes in the P6̅ space group, with the ZrNiP structure type. Quenching experiments and in situ neutron powder diffraction studies were carried out to determine the reaction parameters that favor particular products. Under slow-cooling conditions, BaYbMgSi precipitates from the flux at 800 °C. A faster cooling rate of an identical reaction results in the formation of single crystals of BaYbMgSi in the flux at 640 °C. This indicates that the crystallization of products in this metal flux reaction does not involve precipitation and interconversion of different phases but instead depends on the rate of cooling across the supersaturated metastable zone in this system.