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 approximately 780-degrees to approximately 860-degrees-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-degrees-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 alpha-Al2O3. Their mechanical properties are examined, in connection with microstructures and t/m ZrO2 ratios. Composites with a homogeneous dispersed alpha-Al2O3 derived from solid-solution ceramics result in a remarkable increase of strength.