Geoscience Reference
In-Depth Information
(10,3)
(10,2)
(01,2)
(01,1)
(10,1)
(10,1)
(01,1)
(10,0)
(10,1)
Figure 5.32 Morphology of the GaPO
4
single crystals
[129]
.
Figure 5.33 Characteristic
photographs of GaPO
4
crystals
obtained by the hydrothermal method
[131]
.
γð
0001
Þcγð
0112
Þ
.
γð
1010
Þ
.
γð
0111
Þ
.
γð
1012
Þ
.
γð
1011
Þ
The common twins observed in GaPO
4
are according to the Dauphine, Brazil and
Laydolt's twinning laws. Twinning in GaPO4 has been discussed in great detail in
Ref.
[131]
. Also X-ray topographic studies on GaPO
4
have been carried out by
Capelle et al.
[127] to study twinning in GaPO4 crystals.
5.4.3 Dielectric Properties of Gallium Phosphate
The influence of the growth rate on the quality of the GaPO
4
crystals has been
studied through IR spectrometry by Cochez et al. (1993)
[122]
. As conventionally
done for quartz and berlinite, the (OH)
2
impurity content was monitored by IR
measurements in the wave number range of 4000
2500 cm
2
1
, using the relation:
α
5
1
=
d cm log
ð
T
3800
=
T
3167
Þ
where T
3800
and T
3167
are respectively the transmittances at 3800 and 3167 cm
2
1
,
respectively. The strongest absorption band of Al-OH for berlinite appears at
3291 cm
2
1
is shifted to 3167 cm
2
1
and it
for Ga-OH in case of GaPO
4
(
Figure 5.34
). The
α
values obtained by the authors are 1.6 and 2.2 for two of their
