Non-passive behavior of equivalent circuit components in AC powder electroluminescence (ACPEL) lamps

Abstract

For the first time, the voltage and frequency characteristics of a single layer AC powder electroluminescent lamp have been examined in detail to reveal the individual contributions of the material components involved. Statistical modelling has been employed to refine the equivalent circuit description of the lamp. DC-blocked resistance-capacitance networks can be reduced to a single effective resistance and capacitance in series. The frequency dependence of these two quantities in the range 4–1600 Hz has been used to unravel the behavior of the different underlying resistance and capacitance components at different voltage amplitudes in the range 25–150 V. The resistive contribution, R, of the activated ZnS phosphor is shown to be non-passive, and obeys the form: R(V,f) = R0(V).f−1/3.e−T.f, where V is the applied voltage, f is the frequency and T is a time constant, at all voltages. For both ZnS and BaTiO3, other characteristics indicate the presence of a thinner, non-polarized region within each semiconducting particle located within the particle's crust. A marked change in the characteristics of the different component values occurs between 25 and 50 V, consistent with the onset of light emission, after which smooth changes in all values are observed up to 150 V.