Year-end Sale % OFF 
Abstract
In this article the photoluminescence (PL) and cathodoluminescence (CL) of undoped BaAl2O4 and BaAl2O4 doped with 500 ppm and 3 mol% Eu2+ is described. The most important results from the CL measurements are: (1) Undoped BaAl2O4 manifested intrinsic CL at 460 nm, which increased at low temperature and did not change significantly upon exposure to the e-beam; (2) Doping BaAl2O4 with Eu2+ changed the character of the intrinsic luminescence band: it became more sensitive to temperature variations and the band experienced a blue shift to ∼425 nm; (3) electron beam (e-beam) exposure of Ba0.97Eu0.03Al2O4 at low temperature increased the 425 nm band strongly while the Eu2+ emission at ∼500 nm decreased by about 70%. The Eu2+ emission band was symmetric, indicating that BaAl2O4:Eu has changed to the P6322 phase upon e-beam exposure at low temperature; (4) We have identified the 460 nm band in undoped BaAl2O4 and the 425 nm band in BaAl2O4:Eu2+ with F-centre luminescence, corresponding to the F-centre emission in α-Al2O3. The evidence for the assignment of the 425 nm band in BaAl2O4:Eu2+ is the spectacular increase of the spectral radiance at 425 nm by e-beam exposure at 200 keV and low temperature. A preliminary model is presented that explains the results. The PL from BaAl2O4:Eu2+ quenched at the rather low temperature of 140°C; this observation is explained in terms of thermal ionization of the Eu2+ ion.
Highlights
The late 1990s saw the advent of solid state “white” lighting in the market place
The study presented in this paper focusses on the properties of the intrinsic emission of undoped BaAl2O4 and the 425 nm luminescence band of Ba0.97Eu0.03Al2O4
The results have allowed us to propose a new hypothesis about the origin of the emission band at 425 nm in the PL and CL spectra of BaAl2O4:Eu2+
Summary
The late 1990s saw the advent of solid state “white” lighting in the market place. This was due to the production of white light from the combination of blue light from light emitting diodes (LEDs) with yellow light from a color converting emitting phosphor that was excited by part of the blue light from the LEDs [1,2]. Since there has been continuous effort to find more efficient phosphors with emission bands in the visible part of the electromagnetic spectrum that could be used as colour converting materials in combination with either blue or near UV emitting diodes [1] Such improved or new phosphors would find widespread use in both the lighting and display industries. The first authors measured PL with UV-excitation at 248 nm and thermoluminescence, while the latter authors measured CL spectra Both author groups attributed the broad emission band to native defect state transitions in BaAl2O4. Suriyamurthi and Panigrahi [37] reported the PL at room temperature of undoped BaAl2O4 by excitation with near UV light at 346 nm They recorded a main emission band at 500 nm and a shoulder at 430 nm and tentatively attribute these emission bands to Vk3+ defect centres. Before recording any CL spectra, this material was annealed for 60 hours at 950°C in air; after this treatment it was determined by XRD that the material had the hexagonal P63 structure of BaAl2O4 (∼100%)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
