| The phase transformations in zirconia take place between 900°-1000°
and l200°C while heating, and between 1000° and 800°-t;00°C while
cooling cansing material movement. Hence, effect of amount of CaO
and CaF3 additions and calcination temperature on denslfication and
stabilization was studied by thermal cycling between 1100° and
1oo•c (lower range) and 1400° and 700°C (higher range) up to 25
thermal cycles.
It was observed that higher densification can be obtained by thermal
cycling at lower temperature compared to the temperature required
in normal sintering process, particularly so, with CaO additions.
High density was attained with CaO additions up to 2% compared to
equivalent amount of CaF1 additions in the lower temperature range.
ID general, uncalcined compositions attained high density which decreased
with increasing calcination temperature. Thermal cycling
promoted stabilization. The reaction was almost completed within
5 thermal cycles. |
