Effects of Technique Parameters on Gelating Process of Cordierite Ceramics Derived from Sol-Microemulsion-Gel Method

Nano-Cordierite powders used for high frequency chip inductors (MLCIs) were prepared by the sol-emulsion-gel method. The samples derived from these powders could be sintered at 900°C to be cordierite ceramics having a low dielectric constant and dielectric loss (ε=3.18, tgδ=0.00011; 1GHz). Effects of precursor concentration, treating temperature, and [H2O]/[Si] ratio of this material were studied. The pseudo-ternary phase diagram of sol/TritonX-100/n-hexanol/cy- clohexane was constructed and the influences of each variable on the phase diagram were discussed. Results showed that the optimal precursor concentration, treating temperature, and [H2O]/[Si] ratio for qualifying the gelation of the material were 1.5 mol/L, 45°C, and 4, respectively. Results also showed that for qualifying cordierite powders, the use of TritonX-100 as a surfactant together with n-hexanol as a co-surfactant could dissolve more magnesium nitrate and aluminium nitrate, and obtain a wider W/O micro-emulsion region than when other reagents were used. The samples derived from this method can be co-fired with a silver electrode, an ideal dielectric material for high frequency MLCIs.