Geoscience Reference
In-Depth Information
Figure 10.41 Perovskite-type alkaline earth titanates. (a) See Ref.
[163]
and (b) see Ref.
[172]
.
TiOSO
4
×H
2
SO
4
×H
2
O
TiO
2
×H
2
O
Ba(OH)
2
8H
2
O
Hydrothermal treatment in an autoclave
T
= 170ºC
P
= 0.1-1
MPa
Reaction time = 1-120
h
Dissolution in H
2
O
Adding NH
3
(pH>7)
Washing with H
2
O solvent
Water / 1.5-pentanediol
BaTiO
3
Figure 10.42 Schematic preparation route for lyothermal synthesis of BaTiO
3
[177]
.
precursor is the rate controlling stage. In comparison with those in methanol, the
reactions in MOE for the syntheses of PbTiO
3
powders required higher temperatures
or longer time because of MOE having a lower vaporizing pressure and relative
permittivity.
Kaiser et al.
[177]
have synthesized BaTiO
3
powders at a temperature of 175
C
and pressures between 0.1 and 1 MPa,
starting from TiO
2
xH
2
O and Ba
(OH)
2
8H
2
O in solvents of pure water, 1,5-pentanediol and in different mixtures
of both using the lyothermal method.
Figure 10.42
shows the schematic preparation
route for lyothermal synthesis of BaTiO
3
.
The authors could control the size and habit of BaTiO
3
particles through the vis-
cosity of the solvent and the concentration of the starting materials. The lyothermal
method offers a promising means of producing various nanocrystalline materials of