Geoscience Reference
In-Depth Information
conditions (using Tuttle type of autoclaves). A series of mixed mineralizers like
H
2
SO
4
1
KF in different ratios were
tried in order to bring down the PT conditions of the crystallization of KTP crys-
tals. The pressure in the system was calculated from PVT relations. In the case of
lower PT experiments, the temperature was 275
C and the pressure was approxi-
mately 100 bar. The experiments were carried out for 8
KOH, KF
HCl, HF
KF, H
2
SO
4
1
HCl
1
1
1
10 days and spontane-
ously nucleated small crystals of KTP were obtained. The resultant product was
washed thoroughly in distilled water to remove the excess solvents and the crystals
were collected and dried. The size of the crystals was around 1 mm, colorless,
transparent, and exhibiting a vitreous luster. The faces were developed in most of
experiments. The solubility measurements were carried out on KTP crystals using
the above said mixed mineralizers under hydrothermal conditions.
Figure 5.40
shows the solubility curves for KTP.
Figure 5.41
shows a representative photograph
of a KTP crystal obtained by the hydrothermal method. Similar experiments were
carried out under elevated PT conditions (P
2
325
C). The crystals
were better in quality compared to the crystals obtained under lower PT conditions.
Belt et al. (1989)
[151]
have reported the growth of KTP single crystals in 4 l
capacity autoclaves at temperatures of 475
C and 1.5 kbar. Gold liners were used
here exclusively as corrosion resistance to the phosphates. Baffle openings were
adjusted in the range of 20% with T
500 bar and T
5
5
30
40
C and the total run durations were
5
2
40
50 days. The growth rates sustained were 0.5
1.0 mm/side/week on (011)
2
2
seed crystals
[123]
.
Belt and coworkers from Airtron Division of Litton Systems have increased the
autoclave volume further and developed the low-temperature hydrothermal process
in 5 l systems. These large autoclaves have produced the largest KTP single crys-
tals available in the world (
Figure 5.42
). These crystals are typically 4
8cm
3
5
3
3
1.5 cm
2
apertures and up to 2 cm
long when material is extracted from either side of a seed. The schematic diagram
of the large KTP crystals grown in 5 l autoclaves is shown in
Figure 5.43
. The rect-
angle in the center is seed plate, and the numbers identify prominent planes
[134]
.
and easily provide finished parallelepipeds of 1
2
Figure 5.40 Solubility curves
for KTP
[152]
.
4.2
3.0
1.8
0.6
300
350
400
450
500
550
