PROCESSING AND SOME PROPERTIES OF SHIRASUALUMINA LIGHT WEIGHT COMPOSITES/

Processing and some properties of 28.6 mass% Shirasu/71.4 mass% alumin a light weight composites were studied to develop the dielectric const ant and hermeticity required high performance microelectronic ceramic substrates. Colloidal processing was applied to obtain homogeneous and dense compact of Shirasu (or Shirasuballoons) and alumina. Mixed susp ension of pulverized Shirasu particles (diameter of 8.2 mu m) or Shira suballoons (15 mu m), and alumina particles (0.5 mu m) were prepared b y adding an appropriate amount of polyelectrolyte. The green compacts were sintered at 1300-1500 degrees C for 1h in air. The flexural stren gth of Shirasu/alumina composites sintered at 1400 degrees C showed ma ximum value. Relative dielectric constant of the Shirasu/alumina compo sites was lower than that of the sintered monolithic alumina, which wa s interpreted by a modified Maxwell's equation. Mullite formation was confirmed for the Shirasu/alumina composites sintered at 1500 degrees C by X-ray diffractometer.