Morphology and Stability of Flux Grown Blue Emitting BAM Phosphors for Plasma Display Panels Applications

Abstract

The BaMgAl 10 O 17 :Eu 2+ ͑BAM͒ phosphor is being used as a blue component in plasma display panels ͑PDPs͒ due to its color purity as well as its high luminescence efficiency. When compared to two other components ͑green and red͒, the degradation in brightness of the BAM phosphor is high. To understand the role of morphology in the degradation mechanism, a number of BAM samples with various flux materials, viz., alkali halides along with halides of ammonium and/or aluminum were prepared. In addition to green shift ͑peak maximum shifts toward green͒, the degradation in intensity of these phosphor materials was studied by heating samples in moisture and by exposing them to a high energy Xe flash lamp or Kr excimer lamp. By employing a specific type of alumina as a starting chemical and a suitable flux material in the preparation of the BAM phosphor by solid-state reaction, the green shift could be eliminated and the degradation minimized.Due to its size, shape, and high performance, plasma display panel ͑PDP͒ is gaining considerable attention as a medium for large format ͑ജ65 in.͒ wall-mounted televisions, particularly high definition televisions. Not only the performance but also the life of a PDP is strongly related to the nature of the phosphors and their resistance to energetic discharge ions, electrons, and solarization from VUV arising from the Xe/Ne gas discharge. To improve the overall efficiency of PDPs, efforts are being made to develop new materials, improve manufacturing processes, and design better electronics. Phosphor Laboratory at Panasonic Plasma Display Laboratory of America ͑PPDLA͒ is dedicated to developing better phosphors and also to improving the existing phosphors. 1 In addition to high luminous efficiency, PDP phosphors should have a longer life or stability, required persistence, good color purity, and color temperature. The life of a PDP, in the order of 50,000 h of normal operation is partially related to the performance of the phosphors used in the displays.Presently, divalent europium activated barium magnesium aluminate, BaMgAl 10 O 17 :Eu 2+ ͑BAM͒ phosphor as a blue emitting component is being used in PDPs due to its high quantum efficiency, color purity, and availability. Unfortunately, the BAM exhibits low stability ͑life͒ with VUV flux when compared with the stability of other two phosphor components, viz., red emitting ͑Y,Gd͒BO 3 :Eu 3+ and green emitting ZnSiO 4 :Mn + ͑P1͒, or a blend of P1 and ͑Y,Gd͒BO 3 :Tb 3+ phosphors. The degradation of BAM starts during the baking cycles, part of the manufacturing process and continues during PDP operation. The peak maximum also shifts toward the green during various stages of panel fabrication, known as green shift. The mechanism involved in degradation and a green shift in BAM phosphor is not fully understood. 2-6 It is reported that the BAM with excellent crystallinity and stoichiometric composition shows less degradation. 7 It is also found that the morphology of BAM phosphor particles is also one of the contributors for degradation. 8...

Energy Transfer and Significant Improvement Moist Stability of BaMgAl[sub 10]O[sub 17]:Eu[sup 2+],Mn[sup 2+] as a Phosphor for White Light-Emitting Diodes

“…The flux is generally employed to improve the quality of phosphors. 16,17 The addition of flux plays a role in improving crystallinity, promoting grain growth, and even has a role in controlling the morphology and size of the phosphor. In this work, ͑Ba 0.85 Eu 0.15 ͒͑Mg 0.7 Mn 0.3 ͒Al 10 O 17 , which inhibits better color saturation, was prepared with various fluxes such as AlF 3 , BaF 2 , and H 3 BO 3 .…”