The mechanism of long phosphorescence of SrAl{sub 2-x}B{sub x}O{sub 4} (0<x<0.2) and Sr{sub 4}Al{sub 14-x}B{sub x}O{sub 25} (0.1<x<0.4) co-doped with Eu{sup 2+} and Dy{sup 3+}

Journal Article · Mon Mar 01 00:00:00 EST 2004 · Materials Research Bulletin

DOI:https://doi.org/10.1016/j.materresbull.2003.11.007· OSTI ID:20888024

Nag, Abanti; Kutty, T R N

The role of B{sub 2}O{sub 3} in realizing the long phosphorescence of Eu(II)+Dy(III) doped strontium aluminates has been investigated. IR and solid state {sup 27}Al MAS NMR spectra show the incorporation of boron as BO{sub 4} in the AlO{sub 4} framework of SrAl{sub 2}O{sub 4} and Sr{sub 4}Al{sub 14}O{sub 25}. Phosphor, made free of glassy phases by washing with hot acetic acid+glycerol, did not show any photoconductivity under UV irradiation, indicating that the mechanism involving hole conduction in valence band is untenable for long phosphorescence. EPR studies confirm the presence of both electron and hole trap centers. Dy{sup 3+} forms substitutional defect complex with borate; [Dy-BO{sub 4}-V{sub Sr}]{sup 2-}, and acts as a hole trap center. The electron centers are formed by the oxygen vacancies associated with BO{sub 3}{sup 3-}, i.e. [BO{sub 3}-V{sub O}]{sup 3-}. Under indigo light or near UV irradiation, the photoinduced electron centers are formed as [BO{sub 3}-V{sub O}(e')]{sup 4-}. The holes are released from [Dy-BO{sub 4}-V{sub Sr}(h{center_dot})]{sup 1-} under thermal excitation at room temperature. The recombination of electrons with holes releases energy which is expended to excite Eu{sup 2+} to induce long phosphorescence.

• OSTI ID: 20888024
• Journal Information: Materials Research Bulletin, Vol. 39, Issue 3; Other Information: DOI: 10.1016/j.materresbull.2003.11.007; PII: S0025540803003751; Copyright (c) 2004 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

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTROSCOPY
ACETIC ACID
ALUMINATES
BORATES
BORON OXIDES
DOPED MATERIALS
DYSPROSIUM IONS
ELECTRON SPIN RESONANCE
EUROPIUM IONS
GLYCEROL
HOLES
INDIGO
INFRARED SPECTRA
IRRADIATION
NUCLEAR MAGNETIC RESONANCE
PARAMAGNETISM
PHOSPHORESCENCE
PHOTOCONDUCTIVITY
STRONTIUM
VACANCIES