Nobuyuki Yokosawa

Improvement of Luminescence Degradation of PDP Blue Phosphor with New UV Phosphor

BaMgAl 10 O 17 :Eu 2+ phosphor (BAM:Eu 2+ ) is a useful blue phosphor for plasma display panel (PDP) and fluorescent lamps, but is liable to be degraded by vacuum ultraviolet (VUV) irradiation. We found that YAl 3 (BO 3 ) 4 :Gd 3+ phosphor (YAB:Gd 3+ ) has a high efficiency of emission at 313 nm under VUV excitation and strong resistance to luminescence degradation caused by heat and VUV irradiation. To prevent this degradation, YAB:Gd 3+ is mixed with BAM:Eu 2+ . In this mixed phosphor, the VUV energy absorbed by the former is efficiently transformed to the blue emission of the latter. Consequently, the luminescence degradation inherent in the blue phosphor is decreased with a small sacrifice of the emission intensity.

Vacuum Ultraviolet Excitation Processes of YAl3(BO3)4:R (R = Eu3+, Gd3+ and Tb3+)

The luminescence characteristics of Gd3+, Tb3+ and Eu3+ activated YAl3(BO3)4 phosphors in the vacuum ultraviolet (VUV) and ultraviolet (UV) regions of 130–300 nm are investigated. It is shown that the non activated YAl3(BO3)4 phosphor emits UV light under the VUV excitation, and the emission is related to BO3 atomic-groups. The rate of the energy transfer from the host to the activators is in the order of Eu3+ > Tb3+ > Gd3+.

The Excitation Processes of Sensitized Luminescence in YAl3(BO3)4:Eu3+, Gd3+ Phosphors

The photoluminescence of YAl3(BO3)4:Eu3+ phosphor is sensitized by the codoping of Gd3+ ions under ultraviolet excitation from 130 nm to 160 nm. The Gd3+ ions sensitize the emission of Eu3+ ions by a two-step energy transfer from the host to Gd3+ and then to Eu3+ ions.

30.3: Reduction of Electron‐Beam‐Induced Degradation of ZnS Green Phosphor Coated with Phosphate

Electron-beam-induced luminescence degradation is found to be reduced in ZnS: Cu, Al phosphor coated with a limited low content of phosphate. The behavior of the degradation is correlated with the quantities of SO2 and H2O gases released from the phosphors, analyzed by temperature programmed desorption-mass spectrometry (TPD-MS) and transmission electron microscopy (TEM) observations. We find that the layer coated with the appropriate phosphate content is uniform and continuous, which prevents the surface chemical reactions that cause the degradation.