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Keywords:

  • 64.70.kp;
  • 65.40.–b;
  • 66.10.Ed;
  • 81.05.Je

Abstract

La2−xBixMo2Oy (x = 0, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.1, 0.16, 0.24, 0.3) ceramic samples have been characterized by X-ray diffraction, differential scanning calorimetry (DSC) and conductivity measurements in order to assess the dynamics of the transitions between the low-temperature (α), high-temperature (β) and metastable (βms) phases. Bi doping to x ≥ 0.05 fully stabilizes the cubic phase, suppressing the β[RIGHTWARDS ARROW]α phase transition. In addition, DSC results demonstrate that considerable doping levels give rise to a small thermal event between 450 and 500 °C, which has been identified as the βms[RIGHTWARDS ARROW]β phase transition between cubic phases with static and dynamic oxygen disorder. In this temperature range, the conductivity of the doped materials experiences a transition from Arrhenius to Vogel–Tammann–Fulcher behaviour. Low bismuth concentrations have a significant effect on the conductivity of La2Mo2O9.