Low‐Temperature Sintering of Seeded Sol—Gel‐Derived, ZrO₂‐Toughened Al₂O₃ Composites

Seeding a mixture of boehmite (AIOOH) and colloidal ZrO₂ with α‐alumina particles and sintering at 1400°C for 100 min results in 98% density. The low sintering temperature, relative to conventional powder processing, is a result of the small alumina particle size (∼0.3 μm) obtained during the θ‐to α‐alumina transformation, homogeneous mixing, and the uniform structure of the sol‐gel system. Complete retention of pure ZrO₂ in the tetragonal phase was obtained to 14 vol% ZTA because of the low‐temperature sintering. The critical grain size for tetragonal ZrO₂ was determined to be ∼0.4 μm for the 14 vol% ZrO₂—Al₂O₃ composite. From these results it is proposed that seeded boehmite gels offer significant advantages for process control and alumina matrix composite fabrication.