EFFECTS OF HEAT-TREATMENTS ON MULTILAYER PIEZOELECTRIC CERAMIC AIR COMPOSITES

Ceramic-air composites were prepared from laminated and sintered tapes that contain ceramic powder in a binder matrix and that have carbon-containing "fugitive" inks screened onto them. The resulting laminates contained initially more than 50% by volume of organic material. This had to be eliminated ("burned out") before sintering. The results of thermogravimetric analyses demonstrated the frequent occurrence of exothermic reactions when the burnout was conducted in air. This was prevented by lowering the partial oxygen pressure, but only to a point where reducing conditions were prevented since the latter caused carbonization, incomplete burnout, and increased lead evaporation. This was particularly important when a heavy kiln load consumed a significant fraction of the available oxygen. Weight loss, X-ray fluorescence, and electrical parameter determinations were then used to optimize the burnout conditions. As a result it became possible to make ceramic-air composites that had consistent electrical behavior and that tolerated high hydrostatic pressures.