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and the cost of the experiments involved is rather high. This led to serious efforts
from several groups, particularly with reference to the PVT relations in several
related systems like K
2
O
TiO
2
P
2
O
5
, which ultimately brought down the pressur-
400
C. Similarly
the use of the solvothermal technique along with the organic additives and surfac-
tant havs brought down the pressure
e
temperature conditions to the tune of P
700 bar, T
325
5
5
2
temperature conditions for KTP growth. It
has renewed interest in KTP crystal growth. On the whole, the credit goes to
Laudise and Belt for contributing extensively on the PVT relations of the KTP sys-
tems and also for growing large size single crystals of KTP by the hydrothermal
technique
[24,145
147]
. The earlier hydrothermal experiments on KTP were car-
ried out using platinum- or gold-lined autoclaves with Tuttle seals (cold-cone seal
closures). The crystalline KTP nutrient in appropriate dimensions and quantity was
introduced into the bottom part (dissolution zone), and the seeds (cut in proper
directions) were suspended on a frame in the upper part (growth zone) of the liner
cavity. A baffle separated them so as to control the solution convection for estab-
lishing a suitable temperature gradient. The mineralizers used in the earlier experi-
ments were usually KF and K
2
HPO
4
taken with a definite molarity. The percentage
fill (70
2
80%), percent open area of the baffle (5
10%) and temperature gradient
80
C) were selected appropriately. Under such experimental conditions,
the crystals are usually 16
Δ
(
t
5
10
2
7mm
3
.
At present, several variants of hydrothermal growth of KTP single crystals are
known
[24,145,148
150]
. Laudise et al. (1990)
[148]
have carried out PVT mea-
surements on 2 M K
2
HPO
4
and 2 M K
2
HPO
4
saturated with KTP (
Figure 5.37a
and b
). Zhang et al. (2006)
[149]
succeeded in growing KTP crystals with high
damage threshold by hydrothermal method.
It was important that growth be conducted in the absence of a gas
15
3
3
liquid inter-
face, otherwise seeds in the gas phase do not grow, and bubbling, boiling, and
bumping contribute to poor quality deposition. They made nutrient by the reaction
of KH
2
PO
4
and TiO
2
in platinum at 1250
C. The hydrothermal flux was 1.5
KH
2
PO
4
to 1.0 TiO
2
in gold- or silver-lined autoclaves at P
1.66
1.93 kbar,
5
2
560
C,
70
C. Growth
T
520
and
Δ
T
30
rates
on
(011) were
5
2
5
2
0.2
1.8 mm/week. Laudise and coworkers have discovered much lower PT con-
ditions for KTP growth, permitting the use of ordinary, unlined steel autoclaves in
aK
2
HPO
4
solvent. By using the reaction KH
2
PO
4
1
2
H
2
Oto
form KTP, they carried out a phase stability study, the results of which are shown
in
Figure 5.38
.
Figure 5.38
shows only the water-rich corner of the complete tern-
ary. Everywhere along the line A-H
2
O, mole ratio KPO
3
/TiO
2
5
TiO
2
!
KTiOPO
4
1
1.00, the same as
in KTP. Arrow 1 in
Figure 5.38
, at approximately 65 mol% KPO
3
/KPO
3
1
TiO
2
(KPO
3
/TiO
2
D
1.8), is at or close to the boundary of the phase fields
α
1
KTP and
KTP at 600
. Alpha (
) is not a completely characterized phase, probably less K
than in KTP. The boundary is probably nearly the same position at 500
C. Arrow
2in
Figure 5.38
, at
α
approximately 50 mol% KPO
3
/KPO
3
1
TiO
2
(KPO
3
/
TiO
2
D
TiO
2
(ana-
tase) at 600
C. It coincides with the line A-H
2
O. Arrow 3, at approximately
58 mol% KPO
3
/KPO3
1.0), is the boundary between the phase fields KTP and KTP
1
TiO
2
(KPO
3
/TiO
2
D
1.4),
indicates
that
the boundary
1
