INFLUENCE OF SINTERING AIDS ON SINTERING, MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF AL2O3 CERAMICS

The influence of MgO and/or pentavalent oxides (Ta2O5, Nb2O5) on sinte ring, microstructure and mechanical properties (four-point bending and cyclic fatigue) of alumina ceramics is studied. MgO retards the growt h of Al2O3 grains effectively. In contrast to Ta2O5, the effect of Nb2 O5 on the microstructure of alumina changes from a sintering temperatu re of 1580-degrees-C to 1700-degrees-C because of the formation of a l iquid phose at higher temperatures. The simultaneous addition of MgO a nd Ta2O5 or Nb2O5 makes it possible to lower the sintering temperature and to get a high-dense, fine-grained material. An alumina ceramic wi th improved mechanical properties will be achieved if a homogeneous di stribution of the sintering aids is guaranteed.