Model Constrained Sintering Experiments: Bi-Layers and Cylinder-Filled Rings

When structures that consist of powders of two or more materials, such as low temperature co-fired ceramic packages or a planar solid oxide fuel cells, are sintered, the mismatch in the sintering shrinkage rates between the different materials produces stress, since the faster shrinking materials are constrained by those that shrink at a slower rate. These stresses can lead to the formation of defects such as cracks or shape distortion. Results of recent model experiments to study the constrained sintering in multi-material systems will be discussed for two model geometries. The first geometry is a simple bi-layer consisting of single layers of two different materials bonded together. Results of in situ observation of sintering bi-layers will be presented and discussed in relation to the properties of the individual layers such as their free sintering rates, uniaxial viscosities and viscous Poisson’s ratio. The second geometry studied was that of a ring of one material filled with a cylinder of a second, slower shrinking material. In this case, the results of several variations of this geometry including filling the ring either fully or partly with a rigid, nonshrinking cylinder or with rigid, non-cylindrical shapes will be presented and discussed.