Raman Shift [lcm

Figure 25. Four percent yttria stabilized zirconia (as-received).

Figure 26. Four percent yttria stabilized zirconia, aged 24 hours in 10% H20 at 250°C.

RAMAN SHIFT [l/cm]

Figure 26. Four percent yttria stabilized zirconia, aged 24 hours in 10% H20 at 250°C.

Figure 27. Two percent yttria stabilized zirconia, aged 168 hours in vacuum.

RAMAN SHIFT ll/cm]

Figure 27. Two percent yttria stabilized zirconia, aged 168 hours in vacuum.

Figure 28. Four percent yttria stabilized zirconia, aged 16 8 hours in vacuum.

RAMAN SHIFT [l/cm]

Figure 28. Four percent yttria stabilized zirconia, aged 16 8 hours in vacuum.

from these analytical techniques reinforced each other and supported our findings that water vapor need not be present to initiate t -*■ m transformation.

This work focused on the investigation of monolithic zirconia toughened ceramics and its application to plasma sprayed thermal barrier zirconia coatings is limited. As described by Miller and others, the tetragonal phase formed in plasma sprayed Y203-Zr02 is found to be nontransformable (t'). This t' phase does not appear to be subject to t + m transformation and suggests that plasma sprayed zirconia coatings are not likely to be subject to aging effects.

0 0

Post a comment