Electrical properties of La2Mo2O9/Al2O3 nanocomposites fabricated by microwave sintering method

High density La2Mo2O9/Al2O3 nanocomposite electrolytes were successfully fabricated by microwave sintering method from the nano-scaled La2Mo2O9/Al2O3 powders. Phase formation, microstructure, grain size and electrical properties of the specimens were examined using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and AC impedance spectroscopy. It was confirmed that the composite electrolytes consist of nanocrystalline La2Mo2O9 phase with an average grain size of 70-150 nm and a small amount of crystalline α-Al2O3 phase at grain boundary. With increasing alumina content, the total conductivity at 600 °C of the composite specimens increases at first and then decreases with a maximum value of about 0.024 S/cm appearing at 2.25 mol% alumina. It was suggested that the enhancement of total conductivity of the composites may be ascribed to the improvement of both grain and grain-boundary conduction introduced by the addition of appropriate amount of alumina.