20 30 40 50 60 70 80 90 100 110 120 130 140 150

ANGLE (26)

FIGURE 5: X-RAY DIFFRACTION PATTERN OF SPRAY DRIED POWDER (VENDOR A)

FIGURE 6: X-RAY DIFFRACTION PATTERN OF CAST & CRUSHED POWDER (VENDOR J)

100 X)1

100 X)1

FIGURE 7: X-RAY DIFFRACTION PATTERN OF SINTERED POWDER (VENDOR B)

HOLE I Y0i<s

FIGURE 8: LOH YTTRIUM END OF THE Y20,*Zr0x PHASE DIAGRAM

HOLE I Y0i<s

FIGURE 8: LOH YTTRIUM END OF THE Y20,*Zr0x PHASE DIAGRAM

along with some monoclinic phase. These observations were consistent with the phases predicted by the ZrOj-Y2Oj phase diagram, shown in Figure 8 (11). The spray dried materials are Zr02; therefore, the room temperature phase is monoclinic. In the case of fused Zr02 powder, all of the Yj03 was in solution and, upon cooling (quenching) to room temperature, this material forms the tetragonal phase as predicted by the phase diagram. In the case of the sintered ZrO, powders, the materials reflected in the high temperature equilibrium phases which are tetragonal and cubic. The YjOj content in these phases was controlled by sintering temperature and, depending on this temperature and the cooling rate after the sintering process, these powders were likely to transform the tetragonal phase to monoclinic in addition to the stable cubic phase at room temperature (Table

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