Sol-emulsion-gel synthesis of cordierite ceramics for high-frequency multilayer chip inductors

摘要

Nano-Cordierite powders used for high frequency chip inductors (MLCIs) were prepared by sol-emulsion-gel method. Effects of precursor concentration and [H_2O]/[Si] molar ratio on this material were studied. The sol-emulsion-gel processing of Mg_2Al_4Si_5O_(18) as well as its dielectric property were investigated. Owing to the better packing efficiency and therefore higher surface energy of the freestanding nano-powder, the pressed pellets made by cordierite powder showed 98.6% theoretical density at 900 °C for 2 h. The additive Bi2O3 was utilized to promote the crystallization or transformation to a-cordierite and sintering. The sol-emulsion—gel-derived cordierite ceramics have low dielectric constant (ε=3.0~4.0; 18 GHz) and low dielectric loss (tgδ < 0.001; 18 GHz) and can be co-fired with high conductivity metals such as Au, Ag/Pd internal electrode at low temperature (900 °C), suggesting that it was an ideal dielectric material for high-frequency multilayer chip inductors.