Millimeter wave sintering of ceramics

At the Forschungszentrum Karlsruhe (D), a compact gyrotron system was installed in 1994 to investigate technological application in the field of high temperature materials processing using millimeter waves (mm-waves). Besides the improvement of the system design, research activities are mainly engaged in studies on debindering and sintering of various types of advanced structural and functional ceramics. Due to volumetric heating and enhanced sintering kinetics, the application of microwaves allows a shortening of the processing time, thereby reducing energy consumption. In addition, microwave technology gives the unique possibility of influencing the microstructure and physical properties of the ceramic materials. This article will give an overview of the benefits of the mm-wave technology with respect to the sintering of structural ceramics, such as Al2O3, Si3N4, or TiO2-ZrO2-MgO multicomponent ceramics, nanocrystalline oxide ceramics, as well as PZT piezoceramics as one of the most interesting classes of functional ceramics.