Hydrothermal Growth of Some Selected Crystals - Hydrothermal Technology - page 207

forms are hexagonal, rhombohedral, rod shaped, needle like, and occasionally
rounded. The morphological forms of AlPO 4 mainly depend upon the nutrient compo-
sition and the solvent in action. Data on the dependency of the morphological features,
and the nutrient composition, as well as the solvent used are given in Table 5.7 .
A typical morphology of AlPO 4 is shown in the schematic diagram
( Figure 5.23 ) consisting of major and minor rhombohedral faces. Figure 5.24a and
b shows the characteristic photographs of the berlinite crystals.

Table 5.7 Morphology of Aluminum Orthophosphate Crystals

T ( C) Morphology

Nutrient Composition

Al 2 O 3 1 H 3 PO 4 mineralizer HCl (1.5 M) 280 Hexagonal and rhombohedral

Al 2 O 3 1 H 3 PO 4 mineralizer NaCl (2 M) 300 Rhombohedral

Al 2 (OH) 3 1 H 3 PO 4 mineralizer NaF
(2.5 M)

300 Rods, needles, or acicular

Al 2 O 3 1 H 3 PO 4 mineralizer NH 4 Cl (4 M) 300 Small hexagonal, rhombohedral

and equi-dimensional

Al 2 O 3 1 H 3 PO 4 mineralizer HCOOH
(2 M)

280 Hexagonal and rhombohedral

Al 2 O 3 1 H 3 PO 4 mineralizer NaHCO 3
(3 M)

300 Hexagonal, rhombohedral, and

slightly irregular

AlCl 3 1 H 3 PO 4 mineralizer HC1 (2 M) 270 Hexagonal

Figure 5.23 Morphology of AlPO 4 consisting of
major and minor rhombohedral faces [90] .

c

〈 0001 〉

j

π

〈 1012 〉

r

z

〈 1011 〉

z

〈 0111 〉

m

a 2

〈 0110 〉

m

m

a 1

r 〈 1010 〉

〈 1010 〉

z

r

π