Ruthenium(V) Oxides from Low-Temperature Hydrothermal Synthesis

摘要

Low-temperature (200°C) hydrothermal synthesis of the ruthenium oxides Ca_(15)Ru2O7, SrRu2O6, and Ba2Ru3O9(OH) is reported. Ca_(15)Ru2O7 is a defective pyro-chlore containing Ru~(V/VI); SrRu2O6 is a layered Ruv oxide with a PbSb2O6 structure, whilst Ba2Ru3O9(OH) has a previously unreported structure type with orthorhombic symmetry solved from synchrotron X-ray and neutron powder diffraction. SrRu2O6 exhibits unusually high-temperature magnetic order, with antiferromagnetism persisting to at least 500 K, and refinement using room temperature neutron powder diffraction data provides the magnetic structure. All three ruthenates are metastable and readily collapse to mixtures of other oxides upon heating in air at temperatures around 300-500°Q suggesting they would be difficult, if not impossible, to isolate under conventional high-temperature solid-state synthesis conditions.