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Luminescence in europium-doped titania: Part II. High concentration range of Eu3+

Published online by Cambridge University Press:  31 January 2011

James Ovenstone ,
Philip J. Titler ,
Robert Withnall  and
Jack Silver
James Ovenstone
Affiliation:
Centre for Phosphors and Display Materials, School of Chemical and Life Sciences, University of Greenwich, Island Site, Woolwich, London SE18 6PF
Philip J. Titler
Affiliation:
Centre for Phosphors and Display Materials, School of Chemical and Life Sciences, University of Greenwich, Island Site, Woolwich, London SE18 6PF
Robert Withnall
Affiliation:
Centre for Phosphors and Display Materials, School of Chemical and Life Sciences, University of Greenwich, Island Site, Woolwich, London SE18 6PF
Jack Silver
Affiliation:
Centre for Phosphors and Display Materials, School of Chemical and Life Sciences, University of Greenwich, Island Site, Woolwich, London SE18 6PF
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Abstract

In continuation of our previous work [J. Ovenstone, P.J. Titler, R. Withnall and J. Silver, J. Phys. Chem. B, 105, 7170 (2001)] we report the following results. Amorphous europium-doped titania phosphors (Ti1−3xEu4xO2) were prepared with europium concentrations from x = 0.000397 to x = 0.143. From investigations using photoluminescence (PL), it was deduced that the luminescence was due to a europium/titanium compound rather than from a europium-containing precipitate dispersed within a titania precipitate. PL brightness was shown to increase linearly to a concentration of x = 0.0159 before quenching began, and the rate of increase of brightness dropped. Brightness then continued to rise (almost linearly) from x = 0.0238 to x = 0.143. Under electron beam excitation these phosphors showed weak cathodoluminescence; for the amorphous materials no quenching was observed. For the crystalline materials (prepared by annealing the amorphous materials at high temperature) no red luminescence was observed above a concentration of x = 0.00318; however, some faint red luminescence was observed below this concentration. In addition, some faint blue emission was observed in crystalline samples that had no red luminescence, indicating the presence of small amounts of Eu2+ ions. This was attributed to reduction of the Eu3+ ions in the electron beam. Europium doping was shown to increase the size of the band gap in the amorphous materials, but had little effect on the band gap of the crystalline powders.

Type
Articles
Information
Journal of Materials Research , Volume 17 , Issue 10 , October 2002 , pp. 2524 - 2531
Copyright
Copyright © Materials Research Society 2002

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References

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