Hidetsugu Matsukiyo

Saturation of ZnS:Ag,Al under cathode‐ray excitation

The decrease in efficiency of ZnS:Ag,Al phosphor powders under high cathode‐ray excitation densities has been investigated in a wide range of Ag concentrations (18–1560 ppm) with the Al/Ag ratio fixed at 1.5. Two distinct regions have been observed in this saturation behavior. For low Ag concentrations up to some 100 ppm (mol) saturation is due to activator ground‐state depletion, which manifests itself in a concentration dependence of saturation. For higher doping levels saturation becomes independent on the Ag concentration. Saturation was found to be temperature independent between 83 and 303 K. Diffuse reflectance measurements revealed an onset of optical absorption near 2.8 eV due to Ag incorporation, which continuously increased with Ag concentration giving no evidence for a change in activator incorporation around 100 ppm. Varying the Al/Ag ratio up to 56.2 had no influence on the saturation behavior, while the efficiency at low excitation densities showed a considerable decrease which could not be...

Problems and progress in cathode-ray phosphors for high-definition displays

Abstract The state-of-the-art development of phosphors mainly for projection tubes is reviewed with an emphasis on improvement of degradation by electron bombardment. Oxygen depletion observed for InBO 3 :Tb 3+ ,Zn 2 SiO 4 :Mn 2+ , and Zn 3 (PO 4 ) 2 :Mn 2+ indicates a potential to form oxygen vacancies, which can change into color centers by trapping electrons. Formation of traps is possibly associated with oxidation of Eu 2+ by electron bombardment in Sr 3 MgSi 2 O 8 :Eu 2+ . An impurity ion can also affect the degradation; for example, in Y 3 Al 5 O 12 :Tb 3+ and Y 3 (Al, Ga) 5 O 12 :Tb 3+ , doping of 10 1 -10 2 ppm Yb 3+ or Eu 3+ reduces the degradation. When heat stored in a phosphor layer assists the degradation, a thin layer with dense packing is desirable. In this respect, surface coating techniques as well as the size and shape of phosphor particles are important.

Reduction of degradation of Y3(Al,Ga)5O12:Tb phosphors by Sc doping

Copyright (c) 1997 Elsevier Science B.V. All rights reserved.It was found that introduction of Sc into Y 3 (Al,Ga) 5 O 12 :Tb is effective for reducing the phosphor degradation by electron bombardment. Thermoluminescence (TL) measurements show that no new TL active traps related to Sc are formed in the phosphor lattice. It was also observed that the TL intensity decreases with an increase in Sc concentration. It is proposed that this effect of the Sc doping is related to the more closed packing of the lattice.

Factors Inducing Deterioration of InBO3 : Tb by Electron Bombardment

Deterioration of an InBO 3 :Tb phosphor screen deposited in potassium silicate solution was studied by a demountable apparatus designed to simulate the tube condition. Evolution of oxygen from the phosphor crystal was observed under intense electron irradiation. It was found that the deterioration is accelerated by phosphor screen heating, which depends on the screen weight, packing density, and an amount of silica gel deposited between particles and the surface of the screen.

Nonradiative recombination process in Y2O2S:Eu3+ phosphors

recombination process iii Y2O2S:Eu3 phosphursHajime Yamamoto and Hidetsugu Matsukiyo*Department of Electronics, rCoo Engineering University1404-1, Katakura-cho, Hachioji, Tokyo 192, Japanand*Central Research Liboratory, Hitachi Ltd.P.O.Box 2, Kokubunji, Tokyo 185, JapanABSTRACFA red cathode-ray phosphor, Y2OS:Eu3, shows a large decrease in luminescence efficiency at highexcitation density at room temperature. The luminescence intensity is approximately proportional to the squareroot of the electron-beam current, indicating that a bimolecular-type nonradiative process competes with aradiative process. In undoped Y2OS, broad luminescence bands with peaks at around 35

Improvement on the linearity of blue phosphor: Evaluation of hexagonal ZnS:Ag,Al

ZnS:Ag,Al phosphors were prepared in an H 2 S flow without using flux at various temperatures. A cubic structure (a zinc-blende structure) was obtained for the sample prepared at 900°C, and a hexagonal structure (a wurzite structure) was obtained at 1050-1200°C. The life was improved simply with increasing preparation temperature. The luminous efficacy and the current coefficient had their optimum temperature at 1050°C. They showed similar tendencies related to the preparation temperature. The diffuse reflectance also showed the similar tendency of the preparation temperature dependence. The thermoluminescence measurement showed that the traps at a depths of 1.3 eV (observed below 1050°C) and 1.15 eV (observed above 1050°C) disappeared at a preparation temperature of 1050°C.

Reduction of Electron‐Beam Induced Degradation by Rare Earth Doping in Y 3 ( Al , Ga ) 5 O 12 : Tb Phosphors

An introduction of Yb ions to Y 3 (Al,Ga) 5 O 13 :Tb phosphors is found to be effective in preventing the slow buildup of luminescence during electron-beam irradiation. It was also discovered that discoloration and efficiency degradation in this class of phosphors can be reduced by doping of Yb or Eu ions. Thermoluminescence measurements show that trap states formed by the doping compete with intrinsic lattice defects in capturing free electrons, resulting in the decreased number of the electrons trapped in the color centers. This doping effect is related to the low charge-transfer state energy of the trivalent rare earth ions described above.