The crystal structure of ionic conductor LaxCe1–xO2–x/2

The crystal structure of La3+ substituted CeO2 solid solution (LaxCe1–xO2–x/2) has been investigated by X-ray and neutron powder diffractions. The fluorite structure of CeO2 is still maintained up to x=0.4 composition although La3+ is the largest trivalent rare earth ion. For x⩾0.5 the crystal structure changes to the pyrochloric cation ordering and the remnant La2O3 is unreacted. This structure can, however, be stabilized by Ti4+ addition or thermal treatment.