The effect of electrode materials on TSC of EPR with hard clay

We are investigating the polarization phenomena of ethylene propylene rubber (EPR) with hard clay. In this paper we have investigated the effect of electrode materials on thermally stimulated current (TSC) of EPR, and found that the TSC of EPR with evaporated gold electrodes has three peaks, P₁, P₂ and P₃ which appear around 60, 35 and 20°C, respectively. The P₁ and P₂ peaks are reduced rapidly with decreasing the polarizing temperature Tp from 35 to 9°C, and disappear if Tp<9°C. While the P₃ peak is not clear at higher polarizing temperature because of the large height of the P₁ and P₂ peaks, it appears clearly if Tp<9°C. On the other hand, the TSC of EPR with evaporated aluminum electrodes has two peaks, P₂ and P₃, when Tp<29°C, though it has all the three peaks, P₁, P₂ and P₃ , if Tp=29°C. The P₁ peak depends on electrode materials. The P₂ and P₃ peaks for the sample with aluminum electrodes have almost the same characteristics as that with gold electrodes, being independent of electrode materials. From these results, we show that the P₁ peak is due to space charge polarization, and the P₂ and P₃ are due to interfacial polarization