Effect of Particle Shape on Anisotropic Packing and Shrinkage Behavior of Tape-Cast Glass-Ceramic Composites

In this study, the influence of particle shape anisometry and particle alignment in tape-cast green sheets on the shrinkage behavior of low-temperature co-fired ceramics (LTCCs) was investigated quantitatively. A new method for the characterization of particle shape with the use of a particle image analyzer is presented, and its application to real material systems demonstrated. A commercial LTCC system and three developed composite powders with different average particle sizes were analyzed. After tape casting, particle alignment in the green sheets was analyzed using image analysis of SEM micrographs of cross sections. The investigations showed that the degree of particle alignment correlates significantly with the particle shape and size of the materials. A further increase in particle orientation was seen after the lamination process. Additionally, the powder packing of both single layers and laminates was analyzed by mercury porosity. The anisotropic shrinkage behavior during the sintering process was determined by means of optical dilatometry. The data obtained on the particle morphology, particle orientation in the tapes, and their effects on the shrinkage anisotropy will be discussed.