High-frequency current oscillations in solid dielectrics

Abstract

Experimental evidence is provided that common industrial organic insulators (phenol-impregnated pressboard, bakelite) may exhibit negative differential resistance. Insulators have been subjected to high non-uniform electric fields with maximum values which between 0.2 MV cm-1 and 1.2 MV cm-1 and, according to experimental data, the time-averaged I-V characteristics showed a distinct N-type NDR region, followed by an S-type NDR region, for electric fields near the pre-breakdown region. Various impulse voltages have been applied to solid dielectric and periodic current pulses were received by the anode electrode. An attempt has been made to interpret and correlate the above results with similar phenomena which occur in semiconductors with a negative differential resistance.