Preparation and properties of sodium iron orthooxomolybdates, NaxFey(MoO4)z

Five different crystalline phases are established in the quaternary system Na–Fe–Mo–O with isolated MoO4 tetrahedra: NaFe(MoO4)2, Na3Fe2(MoO4)3, α- and β-NaFe2(MoO4)3 and NaFe4(MoO4)5. The optimized conditions for sample preparation are described together with structural analyses by X-ray and neutron powder diffraction. The observed crystal structures are compared with known structure types. The high-temperature behaviour, thermal expansion, decomposition or congruent melting, is reported together with some preliminary characterisation of oxygen release as requested for catalytic activity in partial oxidation of hydrocarbons. Magnetic properties and antiferromagnetic ordering have been studied by magnetisation measurements and neutron diffraction.

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