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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
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