Effect Of The Additives On The Sintering Behavior Of Yttrium Oxide Based Materials

Yttria is a very promising ceramics for its superior high temperature stability, corrosion resistance, and conductivity. However, its application is restricted for poor mechanical properties and sinterability. As known, the sinterability can be improved and ideal microstructure can be obtained by adding proper additives. Hence, it is very important to investigate the effect of additives on the sinterability of yttria.In present work, the effect of some selected additives on microstructure of samples was surveyed firstly. Then, the influence of content ceria and calcia and heating process on microstructure, the phase composition and mechanical properties were investigated.Main results are listed as the follows:(1) The additive has a great effect on microstructure on yttria. Therein, grain growth can be improved by adding calcia and it can be retarded by ceria. In addition, it should be noted that dropping method is visual to survey the effect of additive on sinterability and it is very efficient to found a proper additive.(2) The sinterability of yttria can be improved effectively by adding small amounts of ceria. However, the relative density of sample is decreased with the increasing of ceria when the amount of ceria is higher than lmol%. On the other hand, the hardness and fracture toughness is improved with the increasing of ceria when the amount of ceria is less than23.1mol%.(3) The sinterability of yttria is obviously improved by adding calcia. The apparent porosity of samples heated at1500℃with calcia is as low as0.2%. However, because of abnormal coarse of grain, the density and hardness is decreased with increasing of calcia and prolonging soaking time when heated at1600℃over5h. In addition, the hydration effect has not occurred in calcia doped samples.