On the transformation toughening of Y-ZrO2 ceramics with mixed Y-TZP/PSZ microstructures

Heat treatment of Y-TZP at high temperatures produces materials with a mixe d Y-TZP/PSZ phase assemblage, which exhibit a unique combination of high me chanical strength and fracture toughness, uncommon in zirconia ceramics. Th e microstructure and crack growth resistance of the Y-TZP/PSZ materials dev eloped by treating at 1650 degreesC in air a fine-grained Y-TZP was studied . XRD as well as Raman spectroscopy results indicate that the obtained micr ostructure allow the retention of large tetragonal grains (up to similar to 4 mum), resulting in both phase transformability enhancement and pronounced R-curve behavior. The large transformation zone, discerned from accurate m easurements with Raman microprobe spectroscopy, sustains the above assessme nt and points out tetragonal to monoclinic phase transformation as the main toughening mechanism in the investigated Y-TZP/PSZ microstructures. This w as confirmed by satisfactory agreement between the transformation toughenin g estimated from numerical analysis and the crack shielding experimentally determined from the R-curve measurements. (C) 2001 Elsevier Science Ltd. Al l rights reserved.