Colloidal processing of Al 2 O 3 ‐doped zirconia ceramics with CaO–P 2 O 5 –SiO 2 glass as additive

Well‐dispersed concentrated aqueous suspensions of Al 2 O 3 ‐doped Y‐TZP (AY‐TZP), AY‐TZP with 5.4 vol% of CaO–P 2 O 5 –SiO 2 (CaPSi) glass (AY‐TZP5) and 10.5 vol% CaPSi glass (AY‐TZP10), with ammonium polyacrylate (NH 4 PA) 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°C‐1500°C. The optimum NH 4 PA 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 behavior was related to the greater amounts of Ca 2+ ions leached out from the CaPSi glass surface. The viscosity of stabilized 40 vol% slips with NH 4 PA 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°C) compared to that of AY‐TZP. AY‐TZP5 exhibited a fine microstructure of tetragonal ZrO 2 (grain sizes below 0.3 µm), and ZrSiO 4 –Ca 2 P 2 O 7 particles homogeneously distributed within the zirconia matrix. It presented similar fracture toughness and a slightly lower hardness compared to those of AY‐TZP.