Oxide powders of (La1.8Dy0.2)(Mo2−xWx)O9 (x= 0.0–1.4)
were synthesized via solid state reaction, using high purity
La2O3 (Aldrich, N99.9%), Dy2O3 (Sigma, N99.9%), MoO3
(Aldrich, N99.5%), and WO3 (Sigma, N99.9%) as reactants.
The moisture in the La2O3 powder was removed by thermal
treatment at 430 °C for 4 h, and it was cooled in a desiccator
before weighing. Stoichiometric amounts of the starting
materials were mixed in a polyethylene jar with agate balls,
then calcined at 830 °C for 10 h. The calcined powders were
ground with a pestle in an agate mortar by hand, uniaxially
pressed into pellets with the assistance of a polyvinyl alcohol
binder. These pellets underwent binder burnout at 500 °C and
were subsequently sintered to high densities in air at 950 °C for
6 h.