Some Aspects of Dielectric Breakdown of Solids

The electric strengths of sodium chloride, polythene, and polymethyl methacrylate were measured using direct and impulse voltages at room temperature. The effects of specimen thickness, electrode radius, and rate of rise of applied field are different in degree from material to material indicating the importance of prebreakdown conditions. It is suggested that the final breakdown mechanism is of the avalanche type, heating by prebreakdown current and the formation of space charges being factors affecting its occurrence.