Starting from a sinter reactive powder prepared by a gel precipitation technique, dense, ultra-fine grained (100–200 nm) yttria stabilized tetragonal zirconia ceramics were obtained by sinter forging at a temperature of 1100 °C or by pressureless sintering at 1150 °C. The pressureless sintered compacts were subjected to further heat treatments at temperatures of 1250–1450 °C or compressive deformation at 1250 °C under uniaxial stresses of 20–100 MPa. The obtained samples were characterized mainly by impedance spectroscopy. After compressive deformation a decrease in grain boundary resistivity was found which increased with applied stress. This can be interpreted in terms of a decrease in impurity segregation and a partial removal by compressive deformation of a poorly conducting amorphous film around the grains. It was also found that the grain boundary resistivity of samples sintered at 1150 °C could be considerably reduced by further pressureless heat treatments at temperatures above 1250 °C. This effect is probably owing to dewetting of the grain boundary and dissolution of grain boundary impurities into the bulk of the grains.
Chen, C. S., Boutz, M. M. R., Boukamp, B. A., Winnubst, A. J. A., & de Vries, K. J. (1993). The electrical characterization of grain boundaries in ultra-fine grained Y-TZP. Materials science and engineering, A168(2), 231-234. https://doi.org/10.1016/0921-5093(93)90732-T