FINE-GRAINED YTTRIA - PROCESSING AND POTENTIALITIES

Fine grained polycrystalline yttria materials were synthesized either by Hot Isostatic Pressing of a 99.995% pure Y2O3 powder or by pressureless sintering with the addition of a small amount of titanium oxide (approximate to 0.2 wt.%). Sintered bodies exhibit a good mechanical resistance up to 1000 degrees C. At higher temperatures, yttria starts creeping and a non-newtonian flow characterized by a stress exponent n approximate to 2 is observed. The smaller the grain size and the lower the brittle to ductile transition temperature. An elongation of more than 40% has been attained above 1400 degrees C for the HIPped material which has the finest grain size.