Phase stability and microstructure evolution of yttria-stabilized zirconia during firing in a reducing atmosphere

The phase transition and microstructure evolution of yttria-stabilized zirconia (YSZ) when firing in a reducing atmosphere are investigated in the present study. As the sintering temperature is lower than 1400 degrees C, the phase observed for the YSZ specimens is the first tetragonal (t) phase with a grain size of only 0.4 mu m in average. When the sintering temperature is increased above 1450 degrees C, the second tetragonal (t') phase appears together with a rapid grain growth rate. A surface layer with grains larger than 20 mu m is observed for the YSZ specimens sintered at 1600 degrees C. It is found that the addition of metallic nickel particles has little influence on the phase transition of YSZ; however, the growth of t'-phase grains is reduced with the addition of Ni particles. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.