Hot isostatic pressing of tetragonal ZrO₂ solid-solution powders prepared from acetylacetonates in the system ZrO₂-Y₂O₃-Al₂O₃

Abstract

In compositions having ZrO₂/Y₂O₃=(74.25−71.25)/(0.75–3.75) (mol% ratio) with 25 mol% Al₂O₃, metastable t-ZrO₂ solid solutions crystallize at ∼ 780° to ∼ 860°C from amorphous materials prepared by the simultaneous hydrolysis of zirconium, yttrium and aluminium acetylacetonates. Hot isostatic pressing has been performed for 1 h at 1130 and 1230°C under 196 MPa using their powders. Two kinds of material are fabricated: (i) perfect ZrO₂ solid-solution ceramics and (ii) composites of ZrO₂ solid solution and α-Al₂O₃. Their mechanical properties are examined, in connection with microstructures and t/m ZrO₂ ratios. Composites with a homogeneous dispersed α-Al₂O₃ derived from solid-solution ceramics result in a remarkable increase of strength.