Mechanical Properties of Hot Isostatically Pressed Zirconia‐Toughened Alumina Ceramics Prepared from Coprecipitated Powders

Amorphous Al 2 O 3 –ZrO 2 composite powders with 5–30 mol% ZrO 2 have been prepared by adding aqueous ammonia to the mixed solution of aqueous aluminum sulfate and zirconium alkoxide containing 2‐propanol. Simultaneous crystallization of γ‐Al 2 O 3 and t ‐ZrO 2 occurs at 870°–980°C. The γ‐Al 2 O 3 transforms to α‐Al 2 O 3 at 1160°–1220°C. Hot isostatic pressing has been performed for 1 h at 1400°C under 196 MPa using α‐Al 2 O 3 – t ‐ZrO 2 composite powders. Dense ZrO 2 ‐toughened Al 2 O 3 (ZTA) ceramics with homogeneous‐dispersed ZrO 2 particles show excellent mechanical properties. The toughening mechanism is discussed. The microstructures and t / m ratios of ZTA are examined, with emphasis on the relation between strength and fracture toughness.