Effect of Ho substitution on the ionic conductivity of La ₂Mo _1.7W _0.3O ₉ oxygen ion conductor

Partial substitutions of Ho at the La-site of La ₂Mo _1.7W _0.3O _9-δ were carried out. Compound La _2-xHo _xMo _1.7W _0.3O _9-δ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5) has been synthesized by solid state reaction technique. The specimens were characterized by XRD, SEM, DSC for crystal structure, surface morphology, phase transition and ac impedance spectroscopy for conductivity and other electrical parameter determination. Partial substitution of Ho at the La-site of La ₂Mo _1.7W _0.3O _9-δ, increases the conductivity within the substitutional range, x ≤ 0.2. The phase transition of La ₂Mo ₂O ₉ is suppressed in doped compound and a transition from Arrhenius to VTF behavior of temperature dependence of conductivity is observed around 500°C. The conductivity is found to be high in the intermediate temperature region and at high temperature the conductivity of La _2-xHo _xMo _1.7W _0.3O _9-δ (0.05 ≤ x ≤ 0.2) is almost similar with that of La ₂Mo ₂O ₉. The decrease in energy barrier enhances the thermally assisted process to start at lower temperature.