Dynamics of energy absorption versus crystallization in Bi{sub 4}Ge{sub 3}O{sub 12} (BGO) amorphous materials
- National Institute of Materials Physics, P.O. Box MG-7, Bucharest-Magurele, Ilfov, 077125 (Romania)
Theoretical and experimental determinations show that the intrinsic luminescence of BGO materials is strongly influenced by GeO{sub 4}{sup -} tetrahedra around Bi{sup 3+} ions. Besides Bi{sup 3+} transitions, the excitonic spectra mask the BGO bandgap. Theoretical computations give the bandgap at 5.19 eV compared with the experimental one at 5.17 eV in BGO crystals and a significant decrease at 3.26 eV in the amorphous materials. This is due to the high disordering of the GeO{sub 4}{sup -} tetrahedral which also reduces the refractive index of the amorphous materials. Formation of excitonic states and their overlap with the Bi{sup 3+} transitions suggests that the energy absorption takes place via the p-electrons of the O{sub 2}{sup -} ions and is then transferred to the Bi{sup 3+}p-electrons (excited states) close to the conduction band. Light emission appears after de-excitation to the ground state.
- OSTI ID:
- 22202836
- Journal Information:
- Materials Research Bulletin, Vol. 45, Issue 10; Other Information: Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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