Ammonothermal Crystal Growth of Germanium and Its Alloys: Synthesis of a Hollow Metallic Crystal

Elemental germanium and other metals, including Cu, In, Ag, Bi, Sn, and In, are transported under acidic
ammonothermal conditions from the hot zone of a sealed quartz tube to the cool zone, where both crystalline and amorphous
materials can deposit. Red amorphous Ge deposits when finely divided Ge that is covered with surface oxide is used along
with NH4Br mineralizer. When the Ge feedstock is mixed with other metals or metal salts prior to heating, crystals of
intermetallic compounds can be grown. Hexagonal crystals of a Cu−Sn−Ge alloy, Cu3Ge, [Sn6O8Ge(NH3)]n, and unusual
hollow crystals of a Ag−Sn−Ge alloy were obtained from these reactions.