PROPERTIES OF ZIRCONIA CERIA HAFNIA ALLOYS

Tetragonal zirconia alloys containing up to 18 mol% ceria and 30 mol% hafnia were prepared by several wet-chemical techniques, sintered to h igh density, and their microstructural and physical properties studied . Toughening in such alloys depends on the retention of the metastable tetragonal phase and the stress required for its transformation to th e monoclinic phase. The degree of metastability of the tetragonal phas e in these ternary zirconia alloys was a function of the relative amou nts of ceria and hafnia present. Such alloying, along with control of grain size, provides an ability to modify the fracture toughness and t he temperature range over which the toughness is optimized.