Multiscale aspects of the influence of yttrium on microstructure, sintering and creep of alumina

Yttrium doping induces modifications of the microstructural features and properties of polycrystalline alumina. This paper presents a review of most results on this topic. Experimental and calculated results on yttrium grain boundary (GB) segregation are first described. They include yttrium distribution as a function of grain size and atomic structural configurations around yttrium in GBs. The role of yttrium on the overall microstructure, GB structure, GB defects and grain growth is discussed. The discussion provides a basis for the understanding of sintering phenomena and creep behaviour. Attention is particularly focussed on the effect of the transition between GB yttrium segregation and the occurrence of GB precipitates on the properties of yttria doped alumina.