CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

peak can be attributed to the crystal field effect on the Er 3+ energy levels. Excitation spectrum
corresponding to 1536 nm emission of Er 3+ ions is shown in Fig.116 (b). It is consist of broad
peak at 255 nm along with sharp peaks at 380, 488 and 522 nm. The broad band is due to the
charge transfer process in WO 2- 4 structural units and sharp peaks are due to f-f transitions of
Er 3+ ion in the CaWO 4 lattice. The appearance of 255 nm band in the excitation spectrum
corresponding to Er 3+ emission indicates that energy transfer is taking place from host to Er 3+
ions.
Intensity (arb.units)
250000
200000
150000
100000
50000
λ exc
255 nm
380 nm
522 nm
0
1400 1450 1500 1550 1600 1650
Wavelength (nm)
(a)
Intensity (arb.units)
14000
λ
12000
em
= 1536 nm
10000
8000
6000
4000
2000
0
250 300 350 400 450 500 550 600
Wavelength (nm)
(b)
Fig.116. (a) Emission spectrum and (b) excitation spectrum of Er 3+ doped CaWO 4
nanoparticles.
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