Process for producing shrinkage-matched ceramic composites

A process for producing a cofired shrinkage-matched composite, said composite comprising at least first and second cofired layers, the process comprising:

• joining the first and second layers of said composite by cofiring and sintering;
• wherein said first layer is a ceramic layer having a first porosity,
• said second layer is in contact with said ceramic layer, and
• said second layer has a second porosity which is different than said first porosity;
• wherein said first and said second porosities are obtained by said cofiring and sintering;
• wherein a first starting material for said ceramic layer has a first shrinkage behavior on sintering, and a second starting material for said second layer has a second shrinkage behavior on sintering, and wherein said first and second shrinkage behaviors are matched such that a difference in linear shrinkage between said first and second layers is from 0 to 1%,
• and wherein the ceramic layer comprises the following compositions (a) or (b):
• (a) at least one ceramic powder (i) comprising individual particles having a size of up to 500 nm, and a ceramic powder (iv) in which primary particles having a size of up to 500 nm are present in the form of agglomerates and wherein the chemical composition of the powders (i) and (iv) is the same;
• or
• (b) at least one ceramic powder (i) as defined in (a) in admixture with at least one powder (ii) comprising at least one sintering-inhibiting substance having a particle size equal to or smaller than that of the powder (i);
• and wherein said second layer is a ceramic or non-ceramic layer.