Low-toxic gelcasting of giant dielectric-constant CaCu3Ti4O12 ceramics from the molten salt powder

• CCTO nano powder was synthesized by a molten salt method in NaCl flux.
• Aqueous CCTO slurry with high solid loading and low viscosity was obtained.
• A low-toxicity monomer, DMAA was used as the gelling agent.
• CCTO green body with homogeneous microstructure and high strength was obtained.
• CCTO ceramics prepared by gelcasting have giant dielectric constant and low loss.

CaCu3Ti4O12 (CCTO) nano powder was synthesized using a molten salt synthesis method in NaCl flux. Synthesis temperature and holding time were investigated. The suitable synthesis condition is 800 °C for 2 h. Aqueous CCTO slurry with high solid loading and low viscosity was prepared by using acrylic acid-2-acrylamido-2-methypropane sulfonic acid copolymer (AA/AMPS) as the dispersant. AA/AMPS dosage and pH condition have been optimized as AA/AMPS dosage of 3 wt% and pH about 9.08. A low-toxicity and water-soluble monomer, N,N-dimethylacrylamide (DMAA) was used as the gelling agent. CCTO green body fabricated by the gelcasting method has the homogeneous microstructure and relatively high mechanical strength of 9.27 MPa. CCTO ceramics obtained by the gelcasting method have higher dielectric constant than those prepared by the cold isostatic pressing method and show relatively low dielectric loss of below 0.2 in the wide frequency range of 102–105 Hz.