However, this solid-state metathesis reaction failed for GaN [37] since GaCl 3 is hydroscopic at ambient temperature. When the metathesis reaction of GaCl 3 and
Li 3 N, Reaction (2), was carried out in benzene at 280
C under pressure in an autoclave, 30 nm GaN nanocrystallites in @80% yield (Figure 7.7(b)) were obtained
[38]. As shown in Figure 7.7(a), the XRD pattern indicates that the product consists mainly of wurtzite-type GaN with a small fraction of rocksalt-type GaN [39].
This rocksalt-type phase with a lattice constant a ¼ 4:100 A ˚
´ , was observed directly
with high-resolution electron microscopy (Figure 7.7(c)). It had been previously
observed at ultrahigh pressure (at least 37 Gpa) via a pressure-induced phase transition from wurtzite-type GaN [40]; when the pressure was decreased to about
25 Gpa, it was transformed into the wurtzite-type GaN again. The size of the asprepared GaN, 30 nm, is beyond its exciton Bohr diameter (11 nm), therefore, no
quantum confinement effect was observed. Using I 2 as a heat sink and diluting
reagents, nanocrystalline GaN was also synthesized from the reaction of GaI 3 and
NaN 3 (Reaction (3)).
GaI 3 þ 3NaN 3 þ I 2 !
380
C GaN þ 3NaI þ 4N 2 þ I 2
ð3Þ
As can be seen in Figure 7.8, the XRD pattern shows that the product is of
Fig. 7.7. XRD pattern (a), TEM (b) and HRTEM (c) images of the GaN nanoparticles.
7 Solvothermal Synthesis of Non-Oxide Nanomaterials
176
Li 3 N, Reaction (2), was carried out in benzene at 280
C under pressure in an autoclave, 30 nm GaN nanocrystallites in @80% yield (Figure 7.7(b)) were obtained
[38]. As shown in Figure 7.7(a), the XRD pattern indicates that the product consists mainly of wurtzite-type GaN with a small fraction of rocksalt-type GaN [39].
This rocksalt-type phase with a lattice constant a ¼ 4:100 A ˚
´ , was observed directly
with high-resolution electron microscopy (Figure 7.7(c)). It had been previously
observed at ultrahigh pressure (at least 37 Gpa) via a pressure-induced phase transition from wurtzite-type GaN [40]; when the pressure was decreased to about
25 Gpa, it was transformed into the wurtzite-type GaN again. The size of the asprepared GaN, 30 nm, is beyond its exciton Bohr diameter (11 nm), therefore, no
quantum confinement effect was observed. Using I 2 as a heat sink and diluting
reagents, nanocrystalline GaN was also synthesized from the reaction of GaI 3 and
NaN 3 (Reaction (3)).
GaI 3 þ 3NaN 3 þ I 2 !
380
C GaN þ 3NaI þ 4N 2 þ I 2
ð3Þ
As can be seen in Figure 7.8, the XRD pattern shows that the product is of
Fig. 7.7. XRD pattern (a), TEM (b) and HRTEM (c) images of the GaN nanoparticles.
7 Solvothermal Synthesis of Non-Oxide Nanomaterials
176