In Situ Characterization of the Shrinkage Behavior of Ceramic Powder Compacts during Sintering by Using Heating Microscopy

Heating microscopy, used as optical dilatometry, provides an advantageous experimental method for characterizing in situ the sintering behavior of ceramic powder compacts. It enables the densification process to be monitored without the application of load, and thus, there is minimal interaction between the sintering sample and external constraints. In this study, the application of the technique in studing the constant-heating-rate sintering of different ceramic powder compacts is shown, focusing on assessing the isotropic or anisotropic shrinkage behavior of the powder compacts investigated. All compacts were made from powders having similar (irreguIar) particle shapes and were obtained by the same uniaxial compaction technique with the use of the same compacting pressures. However, both mullite and yttrium disilicate powder compacts showed isotropic sintering behavior, whereas barium magnesium aluminosilicate glass powder compacts showed shrinkage anisotropy. The complexities in predicting the occurrence of shrinkage anisotropy during sintering and its variation with the progress of densification are outlined briefly.