ZrO ₂ ‐Transformation‐Toughened Glass‐Ceramics Prepared by the Sol‐Gel Process from Metal Alkoxides

Glasses of composition 3ZrO 2 O · 2SiO 2 were prepared by the sol‐gel process from metal alkoxides. Tetragonal ZrO 2 was precipitated by appropriate heat treatment at 1000° to 1200°C. The fracture toughness of these glass‐ceramics increased with increasing crystallite size of the tetragonal ZrO 2 , reaching ∼5.0 MN/m 3/2 at a size of ∼40 nm. The higher fracture toughness was attributed to tetragonal → monoclinic ZrO 2 transformation toughening.