wurtzite-type and the TEM image reveals spherical particles with an average size of
30 nm [41].
AlN nanocrystallites were synthesized via the benzene-solvothermal method
[42], from a mixture of aluminum, I 2 , NaN 3 after reacting at 350
C for 10 h (Reaction (4)).
2Al þ I 2 þ 2NaN 3 ƒƒƒ ƒ!
benzene
350 C
2AlN þ 2N 2 þ 2NaI
ð4Þ
The XRD pattern (Figure 7.9(a)) of the product can be indexed as the hexagonal
AlN, with lattice constants a ¼ 3:1175 and c ¼ 4:9813 A ˚ . TEM (Figure 7.9(b))
shows that the particle sizes range from 5 to 20 nm.
In xylene, 15 nm InAs nanocrystallites (Figure 7.10B) were prepared by zinc coreduction of InCl 3 Á4H 2 O and AsCl 3 at 160
C [43]. The XRD pattern indicates that
the products were sphalerite-type cubic InAs (Figure 7.10A). As shown in Reactions (5)–(8), a trace amount of water resulting from the reactants may be helpful
to the process.
3Zn þ 6H 2 O ! 3ZnðOHÞ 2 þ 6H
ð5Þ
InCl 3 þ AsCl 3 þ 6H ! InAs þ 6HCl
ð6Þ
3ZnðOHÞ 2 þ 6HCl ! 3ZnCl 2 þ 6H 2 O
ð7Þ
InCl 3 þ AsCl 3 þ 3Zn ƒƒ ƒ!
xylene
160 C
InAs þ 3ZnCl 2
ð8Þ
Compounds containing arsenic are usually very toxic, the order of toxicity being
[44]: R 3 As (R ¼ H, Me, Cl, etc.) > As 2 O 3 (As (III)) > (RAsO) n > As 2 O 5 (As(V)) >
R n AsO(OH) 3Àn > R 4 As
þ > As(0). A safer route reacting InCl 3 Á4H 2 O and KBH 4 in
the presence of arsenic was proposed for the preparation of nanocrystalline InAs
[45], see Reaction (9).
Fig. 7.8. XRD pattern (a) and TEM image (b) of the GaN
powders prepared with molar ratios of GaI 3 , NaN 3 and I 2 of
1/4.5/5.
7.2 Solvothermal Synthesis of III–V Nanomaterials 177