Luminescence Thermal Degradation Mechanism in BaMgAl[sub 10]O[sub 17]:Eu[sup 2+] Phosphor

Abstract

BaMgAl 10 O 17 :Eu 2+ ͑BAM͒ blue phosphor was annealed in air at temperatures of 500-1000°C to investigate its thermal degradation. The photoluminescence of annealed samples was studied in ultraviolet and vacuum ultraviolet ͑VUV͒ regions, respectively. The observed Eu 3+ emission revealed that the oxidation of Eu 2+ to Eu 3+ occurred. Moreover, a novel green emission at 513 nm was detected in the VUV emission spectra of annealed BAM. According to the experimental data and results, this green emission was assigned to the migration of Eu 2+ to the spinel block. Therefore, a new and full-scale thermal degradation mechanism is proposed.Plasma display panels ͑PDPs͒ have attracted considerable interest in recent years as components of wall-mounted television sets that are large, flat, and thin. In PDPs, tricolor phosphors are used to convert the vacuum ultraviolet ͑VUV͒ radiation into visible light. BaMgAl 10 O 17 :Eu 2+ ͑BAM͒ is an efficient blue phosphor for PDPs because of its high luminance efficiency under VUV excitation. 1 However, this phosphor undergoes deterioration of color quality and luminance efficiency during the manufacturing process of PDPs in which the phosphors suffer at a temperature of about 500°C in air. 2 This deterioration is one of the most significant shortcomings in the application for the BAMs significant influence on the lifetime and picture quality of PDPs. The key to overcome this problem lies in making clear the unknown degradation mechanism.It has been well reported that the oxidation of Eu 2+ to Eu 3+ was the main cause for the degradation mechanism. 3-7 In contrast, Sohn et al. detected that the thermal degradation was more dramatic than the decreased number of Eu 2+ and suggested that this degradation was not due to the oxidation of Eu 2+ but may be attributed to the local structure change surrounding the Eu 2+ ions. However, no evidence was given in their study. 8 In other words, the thermal degradation mechanism of BAM is still debated and is not well understood.In this study, we investigated the UV and VUV luminescence properties of the annealed BAM phosphor and reported a novel phenomenon discovered in VUV spectra to elucidate the thermal degradation mechanism of this phosphor precisely and in more detail.The results indicate that the migration of Eu 2+ to the spinel block is another essential mechanism of thermal degradation as well as the oxidation of Eu 2+ to Eu 3+ . ExperimentalThe BaMgAl 10 O 17 :Eu 2+ samples were prepared by the traditional solid-state method using BaCO 3 ͑AR͒, MgO ͑AR͒, Al 2 O 3 ͑AR͒, and Eu 2 O 3 ͑99.99% pure͒ as starting materials. The content of Eu was 10% compared to Ba. 9 Stoichiometric amounts of each material were well mixed and calcined at 1600°C for 4 h in a reducing atmosphere ͑5% H 2 in N 2 ͒. The annealing process was carried out at each temperature ͑ranging from 500 to 1000°C͒ for 1 h in air. All pre-and postannealed samples were determined to be single phase by powder X-ray diffraction ͑Rigaku D/max-2400 X-ray diffractometer with Ni-filtered ...

Characterisation of the luminescence properties of BAM:Eu2+ particles as a tracer for thermographic particle image velocimetry

“…Our previous measurements reported in [1] were limited to 700 K because several studies had reported evidence of thermal degradation occurring in BAM:Eu 2+ powder samples after extended (1-h) exposure to temperatures exceeding 770 K [19,20]. Under these conditions, the oxidation state of the Eu 2+ atoms increases to Eu 3+ , resulting in a sharp and permanent drop in the room-temperature emission intensity of the blue broadband phosphorescence.…”

“…According to Refs. [19,30], the 355 nm light should be absorbed in the mO site, while the 266 nm laser should excite the aBR site.…”

The photoluminescence properties of Ba0.95−M B8O13:Eu3+ (M = Ca, Sr, 0 ≤x≤ 0.1) in 100–400 nm regions

“…The excitation spectra had a broad in the region of 180-260 nm which should be the two bands overlapped because of the non-symmetry shape of the excitation band in the spectrum. The one would be attributed to the Ba-O absorption because the many former reports about BAM:Eu 2+ have identified that Ba-O absorption band is about 180 nm [31][32][33]. Except the BAM, the absorption band of Ba-O was also reported in the Ba 2 SnO 4 :Eu 3+ [17].…”

A compact single-camera system for high-speed, simultaneous 3-D velocity and temperature measurements.

“…Thermal degradation was observed for phosphor samples exposed to temperatures exceeding 800 K. The thermal degradation is attributed to the change in oxidation state of Eu 2+ to Eu 3+ and the migration of Eu 2+ in the host lattice [26,27]. This leads to an irreversible decrease in phosphorescence intensity at room temperature and results in inaccurate temperature measurements.…”