Geoscience Reference
In-Depth Information
0
2
4
6
8
1
2
3
10
3
/
T
(K
-1
)
Figure 8.24 Arrhenius plot log
σ
T versus 10
3
/T for Na
2
Ti
3
O
7
crystals
[90]
.
versus 10
3
/T for Na
2
Ti
3
O
7
crystals
[90]
. The activation energy calculated from the
Arrhenius plot is 1.3 eV. The complex impedance measurements show that
Na
2
Ti
3
O
7
represents resonance at about 10 MHz. With a possible modification of
the material, it could be used as a dielectric resonator at 10 Hz.
Nonlinear optical properties of Ti-selenite and Bi
4
Ti
3
O
12
crystals have been
studied in detail and these results have been correlated with other compounds like
Ge- and Si-selenites to investigate the effects associated with photoconductivity.
8.10 Hydrothermal Growth of Lithium Metagallate Crystals
Lithium metagallate, LiGaO
2
, is of special interest because of its high electromechani-
cal coupling constant and acoustic Q. The technology of the growth of lithium metagal-
late has been worked out in detail by Kolb et al.
[91]
. The LiGaO
2
can be obtained by
the Czochralskii pulling and flux methods. However, the flux method does not result in
the growth of large-size single crystals, and also the preferential loss of Li
2
Oatthe
melting point makes it difficult to control stoichiometry in melt-grown crystals. The
initial hydrothermal experiments prompted Marshal and Laudise
[92]
to study the
hydrothermal solubility of LiGaO
2
crystals in NaOH solutions. The experiments have
been carried out in platinum-lined Morey-type autoclaves using 3.5 M NaOH at
T
425
C,
Δ
40
C, percentage fill, 0.7
5
360
T
5
5
0.8. Czochralskii-grown crystals
25
C,%fill0.7
show that under these conditions, the seed melts. The LiGaO
2
nutrient was hydrother-
mally synthesized by reacting 5 M LiOH and 2.5 M Ga
2
O
3
in a short platinum
400
Cand
Δ
have been used as seed. The trial experiments at T
5
T
5
