Effect of transition metal doping on the crystal structure and oxidation state of Sr2MgMo0.9TM0.1O6− 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 Sr2MgMo0.9TM0.1O6−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 Sr2MgMoO6−δ and SMMTM have a face-centred cubic structure in both air and a 5% H2 atmosphere. Thermogravimetric analysis in oxidizing and reducing atmospheres at 800 °C indicated that the oxygen-vacancies concentration (δ) and its variation (Δδ) 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 Mo5+ content in these double perovskites.