Abstract:
In this study, we investigated the effect of sintering atmosphere and temperature on surface
yttria concentration of 3 mole % yttria stabilized tetragonal zirconia polycrystalline
(3Y- TZP) ceramic. The 3Y-TZP ceramic powder was die pressed into discs (20mm
diameter and 5 mm thickness) followed by cold isostatic pressing at 200 MPa. Then the
green compacts were sintered by using tube furnace at air and argon gas atmosphere at
sintering temperatures of 1400 ᵒC and 1500 ᵒC for 2 hours. Yttria concentration was
measured by X- ray florescent analytical microscope (XRF). The elemental composition
was analyzed at twenty different places of the sample using 20 kV, 30 kV and 50 kV as the
X-ray tube voltage. Hydrothermal ageing test was conducted in an autoclave containing
superheated water steam at 180 ℃ and 10 bar for 12 hours to evaluate the aging resistance
of the 3Y-TZP ceramics. That ageing induced tetragonal to monoclinic phase transformation
was calculated by using XRD.
Studies shows that, average yttria concentration increased with increasing X-ray tube
voltage. Thus, the yttria concentration of the sintered sample is increased from surface to
interior. On the other hand, surface yttria concentration decreased with increasing sintering
temperature from 1400 to 1500 ᵒC. However, sintering atmosphere has a relatively weak
influence on the surface yttria concentration.
The ageing studies revealed that the ageing is strongly depend on sintering temperature.
Sample sintered at 1500 ℃ at air and argon atmosphere more susceptible to hydrothermal
ageing. But sample sintered at 1400 ℃ at argon atmosphere shows better hydrothermal
ageing compared to other samples.
