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

Nano-Cordierite powders used for high frequency chip inductors (MLCIs) were prepared by sol–emulsion–gel method. Effects of precursor concentration and [H 2 O]/[Si] molar ratio on this material were studied. The sol–emulsion–gel processing of Mg 2 Al 4 Si 5 O 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 Bi 2 O 3 was utilized to promote the crystallization or transformation to α-cordierite and sintering. The sol–emulsion–gel-derived cordierite ceramics have low dielectric constant ( e =3.0∼4.0; 18 GHz) and low dielectric loss ( tgδ