Effect of transition metal doping on the crystal structure and oxidation state of Sr2MgMo0.9TM0.1O6−δ compounds (TM = Co, Mn or Ni)

Abstract We analyse the effects of the partial replacement of Mo by transition metals (Co, Mn or Ni) on the electronic and structural properties of Sr 2 MgMo 0.9 TM 0.1 O 6− δ (SMMTM; TM is Co, Mn or Ni) compounds. The crystal structure and electronic state adopted by SMMTM compounds at high temperature in oxidizing and reducing atmospheres were studied by the combination of thermogravimetric analysis, X-ray diffraction at high temperature in a controlled atmosphere, X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements. X-ray diffraction patterns at 800 °C showed that Sr 2 MgMoO 6− δ and SMMTM have a face-centred cubic structure in both air and a 5% H 2 atmosphere. Thermogravimetric analysis in oxidizing and reducing atmospheres at 800 °C indicated that the oxygen-vacancies concentration ( δ ) and its variation (Δ δ ) between an oxidizing atmosphere and a reducing atmosphere increase because of TM doping. X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements showed that doping with TM also promotes an increase of the Mo 5+ content in these double perovskites.