CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

strong emission compared to corresponding GaOOH and b-Ga 2 O 3 samples. The low emission
intensity of Tb 3+ in GaOOH can be attributed to the quenching of Tb 3+ excited state due to
hydroxyl groups and that in b-Ga 2 O 3 can be attributed to the formation of Ga 3 Tb 5 O 12 /terbium
oxide phase due to heat treatment at 900°C. The decay curves correspond to 5 D 4 level of Tb 3+
ions in the sample are shown in Fig.37 (b) and measured lifetime values are given in Table 4.
The excited state of Tb 3+ decays single exponentially in GaOOH and a-Ga 2 O 3 and biexponentially
in b-Ga 2 O 3 . These results indicate that Tb 3+ ions are having only one type of
environment in GaOOH and a-Ga 2 O 3 lattices whereas it is more than one type of
environments in b-Ga 2 O 3 . This is further supported by the formation of Ga 3 Tb 5 O 12 /terbium
oxide phase in Tb 3+ doped samples as confirmed by XRD studies.
Intensity (arb.units)
10000
8000
6000
4000
2000
5 D 4
7 F 6
5 D 4
7 F 5
5 D 4
As-prepared
500 o C
900 o C
7
F 4
5 D 4
7 F 3
Normalised intensity
1
0.1
0.01
As-prepared
500 o C
900 o C
0
450 500 550 600 650
(a)
Wavelength (nm)
0 2 4 6 8 10
(b)
Time (ms)
Fig.37. (a) Emission spectra, (b) decay curve corresponding to 5 D 4 level of Tb 3+ in 0.5 at %
Tb 3+ doped GaOOH, α-Ga 2 O 3 and β-Ga 2 O 3 nanomaterials. (λ exc = 255 nm and λ em =
544 nm)
Table 4. Lifetime values corresponding to 5 D 4 level of Tb 3+ from GaOOH:Tb 3+ heated at
different temperatures.
Sample τ 1 (ms) τ 2 (ms)
As prepared GaOOH:Tb 3+ 326 (14%) 1284 (86%)
500°C (α-Ga 2 O 3 : Tb 3+ ) 2389 (100%)
900°C (β-Ga 2 O 3 : Tb 3+ ) 258 (13%) 2872 (87%)
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