Effect of Ho substitution on the ionic conductivity of La2Mo1.7W0.3O9 oxygen ion conductor

Partial substitutions of Ho at the La-site of La2Mo1.7W0.3O9−δ were carried out. Compound La2−xHoxMo1.7W0.3O9−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 La2Mo1.7W0.3O9−δ, increases the conductivity within the substitutional range, x ≤ 0.2. The phase transition of La2Mo2O9 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 La2−xHoxMo1.7W0.3O9−δ (0.05 ≤ x ≤ 0.2) is almost similar with that of La2Mo2O9. The decrease in energy barrier enhances the thermally assisted process to start at lower temperature.

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► Partial substitutions of Ho at the La-site of La2Mo1.7W0.3O9-d were carried out.
► Synthesize and characterization of La2-xHoxMo1.7W0.3O9-d (x = 0 - 0.5) were done.
► Partial substitution of Ho increases conductivity of La2Mo1.7W0.3O9-d for x ≤ 0.2.
► Conductivity is higher than La2Mo2O9 in the intermediate temperature range.
► Higher temperature conductivity is comparable to La2Mo2O9 (beyond 650 °C).