Nontoxic Gelcasting of Nano-SiO2-Doped CCTO Ceramics with Enhanced Dielectric Properties

The development of calcium copper titanate (CaCu 3 Ti 4 O 12 , CCTO) ceramics is often hindered by their high dielectric loss, which limits practical applications. In this work, CCTO powder with tailored micrometer-sized particles, synthesized via a Na 2 SO 4 molten-salt method, was used to fabricate nano-SiO 2 -doped ceramics through an environmentally friendly, water-based gelcasting process with glutinous rice flour as a nontoxic binder. This approach enabled stable slurry processing and effective microstructural control. The incorporation of 3.5 wt.% nano-SiO 2 yielded optimal dielectric performance, achieving a high dielectric constant of 8091 and a significantly reduced loss tangent of 0.08 at 1 kHz; this represents a 71.4% reduction in loss compared to the undoped sample. Microstructural and electrical analyses confirmed that the nano-SiO 2 predominantly segregated at the grain boundaries, forming a continuous amorphous insulating layer. This phase enhanced grain boundary resistivity, optimized the electrical heterogeneity, and substantially improved the frequency and temperature stability of the dielectric properties. This study demonstrates that nontoxic gelcasting combined with nano-SiO 2 doping is an effective and sustainable strategy for tailoring the dielectric properties of CCTO ceramics toward high-performance electronic applications by optimizing the internal barrier layer capacitor structure.