Textural evolution of zirconia and yttria-doped zirconia on thermal treatment under different conditions

Abstract

Abstract Pure zirconia and yttria-doped zirconia samples have been prepared from the corresponding microporous gels under different thermal treatment conditions. Doped materials show a delay in the high symmetry (cubic or tetragonal) to low symmetry (monoclinic) phase transformation, compared to pure ZrO 2 . However, as in pure zirconia, thermal treatment leads to the textural degradation of doped samples. Ageing of gels at 723 K in air yields mesoporous powders. On increasing the yttria content in the sample, adsorption capacity and mesopore surface area decrease and the most probable pore radii are slightly smaller. Differences observed in the porous texture of pure and doped zirconia could be justified in terms of the different packing of the primary particles in the gels. In both pure and doped gels, the evolution of the porous structure is highly affected by the conditions at which thermal dehydration is carried out. Under vacuum, the development of a mesoporous texture is hindered. Condensation and elimination of water produce the most important reduction of the micropore volume.