Effect of the Valence State of Ce Ions on the Phase Stability and Mechanical Properties of the Crystals of Zr[O.sub.2]-Based Solid Solutions

The structure and mechanical properties of the crystals of solid solutions of zirconium dioxide, which are stabilized by yttrium and cerium oxides, have been studied. The electron paramagnetic resonance technique has been used to identify [Ce.sup.3+] ions and to determine their relative concentration in the crystals. It is shown that the presence of [Ce.sup.3+] ions in the crystals is the main factor responsible for their high fracture toughness. The annealings carried out during investigations, which lead to a decrease in the concentration of [Ce.sup.3+] ions, show that a change in the valence state of cerium ions lowers the fracture toughness of the crystals.