Geoscience Reference
In-Depth Information
closer to the mineral baddeleyite.
Figure 9.15
shows the photograph of ZrO
2
crystals
grown under hydrothermal conditions. Today, several variations in the hydrothermal,
solvothermal, and supercritical fluid growth of ZrO
2
crystals include thin films and
the nanosize crystals, for a variety of application have been proposed.
HfO
2
According to Kuznetsov
[86]
, the growth of HfO
2
does not differ much from that of
ZrO
2
. The crystallization of HfO
2
takes place at a higher temperature in KF and NaF
solutions and at still higher temperatures in NH
4
Fsolution(700
C). Again, the major
disadvantage is the higher temperature of crystallization and retrograde solubility.
Hence, in this case also, a horizontally disposed autoclave was used by Kuznetsov
and coworkers
[82,86]
. The autoclave had a transverse baffle in which the orifice
area was
15% of the internal cross-sectional area. Crystals up to 2
2
0.5 mm
B
3
3
Figure 9.15 ZrO
2
crystals grown under
hydrothermal condition.
Source: Courtesy of Kuznetsov
[82]
.
Figure 9.16 HfO
2
crystals.
Source: Courtesy of Kuznetsov
[86]
.