Sintered body of ZrO₂-3.3mass%MgO was prepared, and the bulk density, pore size, transverse-rupture strength (TRS) and the fracture origin were studied in relation with the average particle size ranged from 1.1 to 0.6μm of the powder specimen, which was prepared by an attrition mill with 2-propanol solvent and zirconia ball. The test sample was obtained by sintering at 1680°C×2hr and aging at 1080°C×20hr. TRS was measured by the 3 point-bending and the fracture origin was extensively studied for the samples sintered with three different size particles: 1.1, 0.8 and 0.6μm.
As the particle size was lowered, the bulk density increased from 5.60 to 5.82g/cm³ and both the pore size and its number decreased. TRS of 661, 700 and 623MPa was obtained for 1.1, 0.8 and 0.6μm powders, respectively. Through the observation of transverse-ruptured surface by SEM, the pore was concluded to be responsible as the fracture origin, and the corresponding pore size was measured on each fracture. It was concluded that the 0.8μm sample, in comparison with the 1.1μm sample, increased in TRS by improved solidification and pore size, while the 0.6μm sample lowered in TRS by an over grown grain size in spite of its highly solidified body.