Degradation of ZnS:Cu,Al,Au phosphor powder in different gas mixtures

The ZnS:Cu,Al,Au (P22G) phosphor powder was bombarded by an electron beam in an O-2 ambient, Ar ambient and other mixture of gases. These gases consisted of mixtures of O-2 and COx, and O-2, COx and Ar gas. Auger electron spectroscopy (AES) was used to monitor changes in the surface composition of the P22G phosphor during electron bombardment. When the P22G phosphor powder was exposed to the electron beam in a water-rich O-2 ambient, a chemically limited ZnO layer was formed on the surface. The electron beam degradation of the P22G phosphor powder was also performed in a dry O-2 ambient and a layer of ZnSO4 was formed on the surface. The ZnSO4 formation decayed exponentially with time and it is postulated that this was due to the diffusion of the charge reactants through the ZnSO4 film to the reaction interfaces. The P22G phosphor exposed to the electron beam in an Ar ambient and to the other gas mixtures degraded at a lower rate than in the case of the O-2 ambient. This suggests that Ar and COx may suppress the degradation of the P22G phosphor powder. (C) 2004 Elsevier B.V. All rights reserved.