Low-temperature sinterable cordierite type ceramic powder, preparation

Abstract

The present invention relates to a cordierite (2MgO.2Al.sub.2 O.sub.3.5SiO.sub.2) type ceramic powder sintering at low-temperature defined in that its composition is: 60 to 50% SiO.sub.2, 5 to 20% MgO and 20 to 40% Al.sub.2 O.sub.3, and in that its specific surface area is not less than 50 m.sup.2 /g, this powder having a fritting temperature of less than 1,100.degree. C. The invention also relates to a process for the preparation of this powder, which consists in preparing a mixed alcoholic solution of an aluminum and silicon salt, in preparing a solution of an alcohol-soluble magnesium salt, in mixing the two solutions, in padding a hydrolyzing agent in the form of a totally volatile weak base to the solution, which leads to the formation of a gel, in subjecting the said gel to a first thermal treatment at a temperature not exceeding 450.degree. C., and in subjecting the said powder to a second thermal treatment at a temperature of between 450.degree. C. and 900.degree. C. By a sintering which may be carried out at a temperature lower than 950.degree. C., the powder obtained leads to dielectric ceramics which have a coefficient of expansion less than 1.10.sup.-6 C.sup.-1, and a dielectric constant less than 5.