Teruki Suzuki

Effects of crystallinity on the luminescence of ZnS:Tb,P powder and film

Abstract To investigate the possibility of applying donor (D)-acceptor (A) pair emission in ZnS crystals to electroluminescence (EL) devices, the luminescence properties of ZnS:Tb,P are examined. In the cathodoluminescence spectra of ZnS:Tb,P powder, f-f emission of Tb 3+ ions and D-A pair emission related to Tb donors and P acceptors are observed. It is found that D-A pair emission decreases more easily than f-f emission with degradation in crystallinity. In the cathodo- and electroluminescence of ZnS:Tb,P film, however, only f-f emissions, not D-A pair emissions, are observed. This is because of the lack of good crystallinity in the film. Based on these findings, it is proposed that not only less distortion but also a critical size are required for the observation of D-A pair emission in ZnS films.

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.

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.