It was noted that the addition of a glass phase could control the grain-boundary structure of tetragonal ZrO2 polycrystals. In order to reveal the effect of the glass dopant upon the high-temperature deformation behavior, SiO2-doped, SiO2-Al2O3-doped and SiO2-MgO-doped samples were prepared. Their grain-boundary structures, composition and chemical bonding state were investigated by using high-resolution electron microscopy, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy; with a field-emission transmission electron microscope. It was found that no amorphous film was formed along grain boundaries in any of the specimens. However, amorphous pockets formed at multiple grain-boundary junctions in 3 types of glass-doped specimen. In glass-doped specimens, the segregation of Y, Si and added metal ions (Al3+, Mg2+) was observed over a width of several nm across the grain boundaries. The presence of Si4+ increased the bond overlap population, but Al3+ and Mg2+ decreased it.

Structure and Chemistry of Grain Boundaries in SiO2-Doped TZP. Y.Ikuhara, T.Yamamoto, A.Kuwabara, H.Yoshida, T.Sakuma: Science and Technology of Advanced Materials, 2001, 2[2], 411-24