CaS dopped with rare-earth ions as a kink of powder phosphors has higher luminescent intensity and quantum efficiency.It is also considered CaS phosphors to be direct current electroluminescent material.It is known that in order to be excited by direct current

DCEL phosphor must be covered with surface conducting layer.So the copper-coating process(forming the surface p-type CuxS conducting layer)is important to DCEL.In this paper

a FAAS(Fire atom absorption spectrum)method is used to determine the copper content in the surface of CaS DCEIL powder.The rate of recovery and the relative standard deviation of this method are 99.4%-100.6%

and 0.4%

respectively.The dependence of copper-coating volume on the solution concentration

solution temperature and the processing time was studied experimentally as volume of solution was definite.When temperature of solution and processing time are defined(60)

10min)

fig.1 shows that the greater part of copper ions are changed into CuxS surface-phase when concentration of copper ions is lower

but when its concentration becomes higher

copper-coating volume is saturated.When processing time and concentration of adding copper ions are selected(10min

10mg’g

-1

)

fig.2 shows that copper-coating volume increases with temperature.As temperature goes on the copper-coating volume is adjacent to the content of adding copper ions.Fig.3 shows that the copper-coating volume increases with the increasing of COPper-coating process time and gradually goes to saturate and that speed of this process is gradually slower down(60℃

1.5ing).By means of this method

the preparation process and electroluminescence(EL)properties of CAS were improved.