B. Hoghooghi, J.M. McKittrick, E. Helsel, and O.A. Lopez, "Microstructural Development, Densification and Hot Pressing of Celsian Ceramics from Ion-exchanged Zeolite Precursors," Journal of the American Ceramic Society, 81 [4] 845-852 (1998).

Dense monoclinic celsian ceramics (melting point of 1760°C) have been fabricated utilizing zeolite precursors. A sodium zeolite (Na₈₆Al₈₆Si₁₀₆O₃₈₄H₂O) was ion-exchanged in aqueous solutions to replace Na with Ba ions. The ion- exchanged powders were then heat treated to affect the collapse of the zeolite structure and formation of an amorphous phase at 627°C, followed by crystallization of the celsian ceramic at 990°C. Inducing viscous flow from a thermal soak above the glass transition temperature was necessary to form a dense body from cold pressed powders. Hot pressing at a pressure >5 MPa and above the crystallization temperature resulted in densities >90% of theoretical and eliminated the necessity of adding seed particles to form monoclinic celsian. To fabricate near net shape bodies, the amorphous phase was molded at a temperature just above the glass transition temperature and then crystallized to monoclinic celsian at 1050°C. This processing technique demonstrates the potential of using zeolites as precursors for the low cost, low temperature fabrication of near net shape refractory parts.