Dislocation activity and differences between tensile and compressive creep of yttria doped alumina

A change in the chemical bonding strength and high-temperature creep resistance in Al2O3with lanthanoid oxide doping

“…Cho et al (1997) reported that l000ppm Y-or 500ppm La-doped A1203 had improved creep resistance when compared with undoped A1203 at 1200-1350°C under a stress of 50MPa. Similar dopant effects have been reported by several other groups (Lartigue et al 1993, French et al 1994, Cho et al 1999, Li et al 1999. It has been shown that the high-temperature creep resistance in A1203 with a grain size of 1 pm is markedly improved by doping with a lanthanoid (Ln) oxide such as Y203 or Lu203 even at the level of 0.05mol% (Yoshida et al 1999a).…”

Codoping of Alumina to Enhance Creep Resistance

“…Second, direct measurement of the coefficient of oxygen grain boundary diffusion by Le Gall et al 10 recently showed a 3 orders of magnitude reduction with a doping level of 500 ppm Y, while the oxygen lattice diffusivity increased slightly. Finally, although it has been proposed [19][20][21] that the role of the dopant ions is to modify the grain boundary structure and increase the frequency of special boundaries, recent research by the present group 22 utilizing EBKD (electron backscatter Kikuchi diffraction) has found no evidence of this. This emerging picture of inhibited Coble creep, in turn, implies that blocking effectiveness is essentially a geometrical issue related to dopant size and the local geometry of a particular boundary.…”

Phase and microstructural evolution of yttrium-doped nanocrystalline alumina: A contribution of advanced microscopy techniques

“…Among them, the most effective ones seem to be the trivalent cations, such as yttrium: in fact, due to their ionic radius larger than the aluminium one, they segregate at alumina grain boundary and reduce the intergranular diffusion. [4][5][6] Moreover, if yttrium content increases up to saturation, 7 Y 3 Al 5 O 12 (YAG) precipitation at alumina grain boundaries occurs and dramatically improves both room and high-temperature mechanical properties of the matrix. [8][9][10][11][12] By keeping in mind the several beneficial effects of YAG on the fired microstructure and on the overall mechanical behavior of alumina, in some previous works 13, 14 we have set-up an innovative and easy process for the production of alumina-YAG nanocomposites.…”