The invention relates to a method for producing ceramic components that includes:                a) providing a dispersing agent consisting of at least one first and one second powder fraction of an oxide ceramic, as well as a third powder fraction of an inter-metallic compound in a liquid;        b) forming of a green body with the aid of precipitation by electrophoresis from the mixture; and        c) sintering of the green body in an oxidizing atmosphere to form a ceramic component.        
In particular, the concept of the inventive method is used for producing dense ceramic molded bodies through shrinkage-reduced sintering, preferably a reaction sintering of green bodies.
Shrinkage-reduced sintering processes are distinguished in that after the sintering process, the components to be produced exhibit no change in shape or only a slight change in shape as compared to the green bodies.
The principle of the so-called reaction sintering process is based on minimizing the shrinkage occurring during the sintering process through volume-increasing reactions, e.g. oxidation reactions of metals and inter-metallic compounds. Best known among these are the RBSN (reaction bonded silicon nitride) and the RBAO (reaction bonded aluminum oxide) methods on the basis of silicon and/or aluminum. The primary disadvantage of these two methods is that the ceramic products either still contain residual porosity (in particular with the RBSN method) or, if densely sintered ceramics can be obtained through specific variants, such as SRBSN (sintered RBSN), the shrinkage can only be minimized as a result of the relatively small volume expansion and cannot be completely compensated. The reaction-sintered ceramics based on inter-metallic compounds have advantages in that case.
Shrinkage-reduced sintering methods are particularly suitable for producing prototypes or structured and/or true to form components, which require high dimensional accuracy. In particular with micro components where a subsequent processing is not possible because of the small dimensions, the reaction sintering methods distinguish themselves. However, even for the reconstruction of teeth or tooth components such as crowns or fillings, an individually formed green body should not experience any undesirable deformation during fitting operations, nor should it become larger or smaller during the subsequent sintering.
A method for producing ceramic molded bodies for use in the field of dentistry is disclosed in German patent document DE 100 49 974 A1. With this method, a green body is initially formed and is then sintered. The starting material for producing the green body is a mixture of a ceramic and a metal powder, which is then formed into a green body, preferably with the aid of precipitation by electrophoresis. The sintering occurs under oxidative conditions, wherein the metal powder is oxidized to metal oxide, which results in minimizing the sintering shrinkage. A density of more than 90% of the theoretical density is listed for the sintered ceramic component, which is not sufficient for dental use. As a result, an additional infiltration with glass particles is proposed for closing the remaining pores.
Starting with this premise, it is an object of the present invention to modify a method for producing ceramic components so that it is especially suitable for producing structures and/or true to form components. These components in particular should have a high density above 95% and preferably above 97%, so as to permit the use as mechanically and chemically stable structural ceramics, e.g. for dental applications, wherein the subsequent closing of the residual porosity with glass particles is no longer necessary.