Abstract
Gas-pressure sintering is the most widely used process for manufg. high-performance silicon nitride ceramics. The interaction between the sintering atm. and the silicon nitride ceramics is often featured by an inhomogeneous gray coloration of the near surface area and a gray coloration of the bulk material. In Part I of this work the dependence of the color of the material on the sintering parameters was investigated exptl. It was shown that silicon inclusions having sizes ranging from a few nm up to several .mu.m cause the coloration of the material. Gas pressure, temp. and sintering time influence the formation of the inhomogeneous gray coloration.