Phase relations in ZrO 2 –La 2 Zr 2 O 7 –Y 2 Zr 2 O 7 system

The phase relations in the system ZrO₂–La₂Zr₂O₇– Y₂Zr₂O₇ have been investigated using X-ray diffraction. Mixed oxide phase assemblages were prepared by hydrolysing zirconium butoxide with solutions of Y and La nitrates, followed by drying, calcining, and sintering. The cubic zirconia phase can accept into solid solution the larger, non-cubic stabilising lanthanum ion in the presence of a suitable proportion of the cubic stabilising oxide of yttrium. As the amount of the larger rare earth element ion is increased formation of pyrochlore and tetragonal type compounds is favoured.