Effect of small amount of alumina doping on superplastic behavior of tetragonal zirconia

摘要

The effect of Al2O3 doping of around 0.1wt% onsuperplastic behavior was studied in 3mol% yttria-stabilizedtetragonal zirconia polycrystal (TZP) which was free from SiO2contamination and had a grain size of 0.4μm. Compression creeptests revealed that high-purity TZP with less than 0.07wt%Al2O3had two deformation regions: the low stress region had a stressexponent of three and an apparent activation energy of 640kJ/mol,and the high stress region had two and 460kJ/mol. On the otherhand, TZP containing more than 0.12wt%Al2O3 had only oneregion which had a stress exponent of two and an activation energyof 480kJ/mol. The region of diffusion control with a stressexponent of one was not observed in any samples. High resolutiontransmission electron microscopy revealed that no amorphousgrain boundary phase was produced even with 0.18wt%Al2O3doping. Energy dispersive X-ray spectroscopy near grainboundaries revealed that yttrium was segregating at the grainboundaries with denuded zones of 30nm width, which werecreated during slow cooling from the sintering temperature.