Highly reliable yttria-stabilized zirconia prepared by direct coagulation casting-high valence counter ions using calcium polyphosphate

Ceramic components with high reliability are crucial to engineering applications. Direct coagulation casting via high valence counter ions using submicron calcium polyphosphate as coagulating agent was presented. Tri-ammonium citrate was used as dispersant to prepare electrostatic stabilized YSZ suspension with high solid loading and low viscosity. Calcium polyphosphate with average particle size of 0.18 μm and a narrow particle size distribution was prepared. Glycerol diacetate was used to tailor the pH value of the suspension by hydrolysis to produce acetic acid which helps to decompose calcium polyphosphate and release of calcium ions. It is indicated that the viscosities of suspensions with the addition of calcium polyphosphate suspension and glycerol diacetate are high enough for in-situ coagulation casting at 60-70°C within 20 minutes. YSZ suspension with 3 vol% calcium polyphosphate suspension and 1 vol% glycerol diacetate treated at 60°C could be coagulated within 20 minutes and the compressive strength of the wet samples is 2.64±0.35 MPa. Dense YSZ ceramics with relative density above 98.9% and flexural strength of 826±48 MPa and Weibull modulus of 21 had been prepared.