Colloidal processing of Al2O3-doped zirconia ceramics with CaO–P2O5–SiO2 glass as additive

Abstract

Well dispersed concentrated aqueous suspensions of Al2O3-doped Y-TZP (AY-TZP), AY-TZP with 5.4 vol% of CaO-P2O5-SiO2 (CaPSi) glass (AY-TZP5) and 10.5 vol% CaPSi glass (AY-TZP10), with ammonium polyacrylate (NH4PA) dispersant were prepared to produce slip cast compacts. The rheological properties of 35 and 40 vol% slips were studied. The densification, microstructure as well as hardness and fracture toughness were investigated as a function of CaPSi glass content at 1300-1500 oC. The optimum NH4PA concentration of 35 vol% AY-TZP5 and AY-TZP10 slips at pH ~9 was found to be about 43 and 67 % greater than that of AY-TZP slips, this behaviour was related to the greater amounts of Ca2+ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH4PA attained a minimum value at 5.4 vol% CaPSi glass addition, and resulted in a more dense packing of cast samples. AY-TZP5 can be sintered at a lower temperature (1300 oC) compared to that of AY-TZP. AY-TZP5 exhibited a fine microstructure of tetragonal ZrO2 (grain sizes below 0.3 m), and ZrSiO4 - Ca2P2O7 particles homogeneously distributed within the zirconia matrix. Its presented similar fracture toughness and a slightly lower hardness compared to those of AY-TZP.