Preparation of sub-micron porous yttria-stabilized ceramics with ultra-low density by a TBA-based gel-casting method

► Sub-micron porous YSZ ceramics with ultra low density were fabricated by a new gel-casting. ► The shrinkage could be controlled at a very low level. ► A uniform pore size distribution and novel 3D-framework structure were observed. ► Comparing with water-based gel-casting, TBA-based gel-casting can be used in slurries with ultra low solid loading. ► The porosity of obtained nano-porous zirconia ceramics is high, up to 76.8%, which is difficult to obtain by other methods. Sub-micron porous yttria-stabilized zirconia (ZrO 2–5 mol% Y 2O 3, YSZ) ceramics with ultra low density were successfully fabricated by a novel tert-butyl alcohol (TBA)-based gel-casting method. In this work, polymerization of acrylamide was realized in tert-butyl alcohol (TBA)/ZrO 2 slurries with solid loading ranging from 10 to 30 wt.%. Green bodies with ultra-low density (from 1.18 to 1.65 g/cm 3) could be dried with very small shrinkage (from 0.36% to 0.10%), and relatively high bending strengths (from 26.26 to 112.92 MPa) were achieved. By choosing different initial solid loadings, the green bodies were sintered at different temperatures and subsequently characterized in terms of both microstructure and properties to study effects of solid loading and sintering temperature. Both microstructure and properties exhibited obvious dependence on solid loading. By setting the solid loading (20 wt.%) and changing the sintering temperature from 1350 to 1500 °C, the porosity of the sintered samples varied within the range of 69.9% and 54.1%, as the linear shrinkage varied from 15.8% to 25.2% and pore sizes from 0.58 to 0.44 μm. Due to the neck formation between particles, there were also some smaller pores around 1.7 and 3.0 nm. But the most important characteristics of the porous structure were the uniformity and the interconnection of pores with sizes about 0.5 μm.