Oxidation of Eu in BaMgAl/sub 10/O/sub 17/:Eu/sup 2+/ blue phosphor for plasma display panel (PDP)

The blue phosphor, BaMgAl/sub 10/O/sub 17/:Eu/sup 2+/ showing a blue emission band at,about 450 nm were prepared by solid state reaction of BaCO/sub 3/, Al/sub 2/O/sub 3/, MgO and Eu/sub 2/O/sub 3/ with AlF/sub 3/ as a flux. The thermal quenching of BaMgAl/sub 10/O/sub 17/:Eu/sup 2+/ phosphor significantly reduces the intensity of the blue emission. It is reduced by an amount of 50% after heating at around 800/spl deg/C for 1 hr. The red emission in the 580/spl sim/720 nm region of /sup 5/D/sub 0//spl rarr//sup 7/F/sub 1/ and /sup 5/D/sub 0//spl rarr//sup 7/F/sub 2/ transition of Eu/sup 3+/ is produced from the phosphor heated above 1,100/spl square/. The EPR spectrum also reveals that some part of Eu/sup 2+/ ions are oxidized to trivalent ions above 1,100/spl square/ at around 90 and 140 mT. This oxidation evidence is also detected from XANES absorption spectra for L/sub 111/ shell of Eu ions: an absorption peak is at 6,977 eV of Eu/sup 2+/ and 6,984 eV of Eu/sup 3+/. The combined X-ray and neutron data suggests that the new phase of EuMgAl/sub 11/O/sub 19/ magnetoplumbite structure may be formed by heat treatment.