Grain size dependent residual microstresses in submicron Al2O3 and ZrO2

X-ray measurements of lattice spacings are used to determine residual microstresses present in sintered alumina and in tetragonal zirconia polycrystals due to thermal expansion anisotropy (TEA). In Al2O3 with grain sizes larger than 1 mym the microstresses are 30-100 MPa, in submicrometer samples the grain size influence becomes small and residual stresses range between 20 and 30 MPa. For the grain sizes between 0.3 and 9 mym there is no indication of a change in the high-temperature relaxation mechanism. In ZrO2 with grain sizes of 0.5-1 mym the residual stresses are similar as observed in Al2O3 (20-60 MPa), they decrease further at grain sizes 0.2-0.4 mym. The results are independent of technological approaches like powder processing or sol/gel used to produce the sintered bodies.