Induced Conductivity and Light Emission in Different Luminescent Type Powders

Abstract

The currents induced in various (Zn:Cd)S luminescent-type powders by ultraviolet radiation have been investigated as well as the quenching and stimulating effects due to infrared radiation. Similar experiments on the fluorescent emission have also been carried out. Currents induced in these powders by high energy particle radiation is also described. A model is proposed which contains two types of electron traps, deep traps and shallower traps (which are associated with the emission levels at the activator), and a coupling between the deep traps and the emission levels is assumed. Theoretical calculations based on this model are compared to the experimental results for stationary and nonstationary behavior. This comparison shows that in all (Zn:Cd)S powders investigated, traps exist from which so-called "direct transitions" to the activators occur with negligible contribution to the conductivity. These transitions may not be radiative, and they also occur in materials which exhibit no noticeable light-stimulation by infrared radiation.