Copper(II) silicates and germanates with chain structures II. Crystal chemistry *

Abstract

Abstract Investigations in the system CuO – CaO – MgO – SiO2 –GeO2 revealed the compounds CaCuGe2O6 and CuMgSi2O6. Both have clinopyroxene structure, but different cation distributions with M2 = Ca, M1 = Cu and M2 = Cu, M1 = Mg, respectively. CaCuGe2O6 has a polymorphic transition into a different pyroxene variety at 275 °C. No further Cu pyroxenes could be synthesized with other cations. In CuGeO3, which is unique in having an einer single chain, up to 40% Ge could be substituted by Si, but the pure silicate was not obtained.