SOL-GEL SYNTHESIS OF NANOPHASE YTTRIA-STABILIZED TETRAGONAL ZIRCONIA AND DENSIFICATION BEHAVIOR BELOW 1600-K

The hot-pressing behavior of nanophase, 3-mol%-yttria-stabilized, tetragonal zirconia (Y-TZP) was studied in the temperature range 1290 to 1570 K. Powder was sol-gel synthesized using zirconium tetrachloride and hydrated yttrium chloride precursors. After drying and calcination, the particle size was 40 nm, coarsening to 70 nm upon subsequent annealing at 1273 K. On compact heating at 23-MPa applied stress, densification initiated near the calcination/annealing temperature. Theoretical density was obtained at densification temperature above 1490 K with particle coarsening consistent with classical coarsening kinetics. Microstructural change accompanying densification involved formation of dense regions 2 to 4 mum in size separated by irregularly shaped porous regions. The observed densification behavior complements calculated densification maps for fine-particle Y-TZP.