Oxidation of Eu in BaMgAl10O17:Eu2+ blue phosphor for plasma display panel (PDP)

The blue phosphor, BaMgAl₁₀O₁₇:Eu²⁺ showing a blue emission band at,about 450 nm were prepared by solid state reaction of BaCO₃, Al₂O₃, MgO and Eu₂O₃ with AlF₃ as a flux. The thermal quenching of BaMgAl₁₀O₁₇:Eu²⁺ phosphor significantly reduces the intensity of the blue emission. It is reduced by an amount of 50% after heating at around 800°C for 1 hr. The red emission in the 580∼720 nm region of ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transition of Eu³⁺ is produced from the phosphor heated above 1,100□. The EPR spectrum also reveals that some part of Eu²⁺ ions are oxidized to trivalent ions above 1,100□ at around 90 and 140 mT. This oxidation evidence is also detected from XANES absorption spectra for L₁₁₁ shell of Eu ions: an absorption peak is at 6,977 eV of Eu²⁺ and 6,984 eV of Eu³⁺. The combined X-ray and neutron data suggests that the new phase of EuMgAl₁₁O₁₉ magnetoplumbite structure may be formed by heat treatment.