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Abstract:
Low-temperature (200 degrees C) hydrothermal synthesis of the ruthenium
oxides Ca1.5Ru2O7, SrRu2O6, and Ba2Ru3O9(OH) is reported. Ca1.5Ru2O7 is
a defective pyrochlore containing Ru-V/VI; SrRu2O6 is a layered Ru-V
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 500K, 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 degrees
C, suggesting they would be difficult, if not impossible, to isolate
under conventional high-temperature solid-state synthesis conditions.
