Effect of microstructure on electrical and mechanical properties of La5.4WO12-delta proton conductor

The relationships between microstructural characteristics and electrical as well as mechanical properties of La5.4WO12-delta (LWO54) materials were studied. Polycrystalline LWO54 samples revealed identical transport mechanisms regardless of the sample microstructure. The studied samples show predominately proton conductor behaviour below 800 degrees C and become predominant n-type and oxygen ion conductors above this temperature. The magnitude of the total conductivity is enhanced with larger grain size and lower porosity. Young's modulus decreased by 20% with increasing temperature up to 1000 degrees C regardless of grain size and atmosphere. Fracture strength was determined via ring-on-nng bending tests, yielding values that strongly depended on microstructural characteristics and homogeneity of the microstructure. Elevated temperature deformation studies revealed that creep is governed by cation diffusion mechanism.