Structural and conductivity studies of Y10−xLaxW2O21

The aim of this work was to determine structural parameters of the Y10−xLaxW2O21 (x=0–10) solid solution series and investigate their electric properties. Crystallographic data shows a gradual increase in symmetry with increasing La content, as the structure evolves from orthorhombic, Y10W2O21, towards the pseudo-cubic structure of Y5La5W2O21. The solubility limit of La2O3 was found to be 50% (x=5). Above this level two phases were observed, La6W2O15 and (La,Y)10+xW2−xO21−δ. The conductivity of Y rich samples was very low, with σ of the order 2×10−5–5×10−5 S cm−1 at 1000 °C, whilst ionic conductivity was observed for most La rich doped samples. The highest conductivity was observed for La10W2O21 and its doped analogues, at 1×10−3–5×10−3 S cm−1 at 1000 °C. Unit cell parameters were determined as a function of temperature from 0 to 1000°C, and thermal expansion of these materials was determined from temperature studies carried out at the Australian Synchrotron facility in Melbourne, Victoria, Australia.