Alumina Segregation at Grain Boundaries in Superplastic Y-TZP

Abstract

3mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) with various levels of Al 2 O 3 doping and free from SiO 2 contamination were prepared and the supcrplastic behavior and the microstructures were examined. High-purity TZP with less than 0.07wt%Al 2 O 3 had two deformation regions: the low stress region had a stress exponent of three and an apparent activation energy of 630 kJ/mol, and the high stress region had correspondingly two and 460 kJ/mol. On the other hand, TZP containing more than 0.12wt%Al 2 O 3 had only one region which had a stress exponent of two and an activation energy of 480 kJ/mol. High resolution transmission electron microscopy revealed that no amorphous grain boundary phase was produced even with 0.18wt%Al 2 O 3 doping. EDS analyses near grain boundarics revealed that Y segregated at the grain boundaries with denuded zoncs of 30 nm width that may be created during cooling from the sintering temperature.