Spontaneous coagulation casting (SCC) is a novel in-situ ceramic forming method, involving an anion dispersant which acts as both dispersing and coagulating agent and works well at room temperature in air. Ceramic particles in a slurry prepared by SCC participate in the formation of organic network which is originates from hydrophobic interaction and hydrogen bonding among the dispersant molecular chains, quite different from other gelcasting systems. The ceramic gel formed by SCC is a physical gel and the formed organic network among ceramics particles possesses low density which is conducive to water transportation and stress relaxation during drying.

The research progress in the preparation of transparent ceramics by SCC over the last decade is reviewed in this paper, mainly including powder dispersion and high solid loading slurry preparation, slurry solidification and drying, densification of green bodies, and preparation of large size and high optical quality transparent ceramics. It involves translucent alumina, and hightransmittance transparent alumina ceramics, yttrium oxide, AlON, yttrium aluminum garnet and MgAl₂O₄ transparent ceramics. For the transparent alumina ceramics, the shear force in the flow of slurries during casting was used to horizontally arrange alumina platelets in the slurry of equiaxed alumina grains, grain orientation occurred through the platelet as templates during sintering. Alumina single-crystal-like structure formed and high transmittance alumina ceramics resulted. For yttria and AlON transparent ceramics, before SCC yttria and AlON powders were respectively treated with organic compounds to ensure them hydrophobic and water resistant because the powders easily react with water which changes the chemical composition of the powders and decreases solid loading of the slurries.

More recently, MgAl₂O₄ transparent ceramics with a dimension of 470mm×235mm×10 mm was successfully prepared by SCC and vacuum sintering. SCC has become a universal method for preparing transparent ceramics, which is promising in preparing transparent ceramics with complex shapes and high optical quality.

A green body with a density as high as possible is critical to diminish the crisis of deformation or cracking when large-size parts are sintered. Here, a new method, i.e., re-fluidising the aged ceramic gel is developed to prepare the high-density green body. Alumina slurry with 56 vol% solid loading and copolymers of isobutylene and maleic anhydride were aged without vaporisation and re-fluidised by non-intrusive shearing after removing the exuded water. The re-fluidised slurry was re-casted. The resultant wet gel was dried and deboned at a low temperature. The relative density of the obtained green body was 64.6%, 1.5% higher than that without aging and re-fluidising. The linear sintering shrinkage of the body decreased by 0.7%. The enhanced green density is explained from the viewpoint of the solid loading and the structure of the slurry.