The paper by Clarence Zener, titled "A Theory of the Electrical Breakdown of Solid Dielectrics," explores the mechanisms behind the sudden increase in current during dielectric breakdown in solid materials. The author begins by discussing the Bloch model of metallic conduction, where electrons move freely in a periodic lattice, and energy levels are grouped into bands. In insulators, these bands are fully occupied, but thermal excitation can introduce a few electrons into the upper, unfilled bands. The first mechanism for dielectric breakdown involves electrons being excited to higher energy levels by an external electric field, leading to an exponential increase in the number of electrons in the upper band. The second mechanism, which is the focus of this paper, involves the auto-ionization of free electrons in the presence of a strong electric field, similar to the auto-ionization of free atoms in gases. Zener uses the Bloch model to calculate the rate at which electrons transition from the lower to the upper energy bands under a constant electric field. He derives an expression for the probability of transition per unit time, which depends on the energy gap between the bands and the electric field strength. The theory predicts that dielectric breakdown occurs suddenly when the electric field reaches a critical value, consistent with experimental observations. The breakdown field magnitude and the suddenness of the breakdown are both explained by this second mechanism. In the discussion, Zener notes that the results obtained for a one-dimensional lattice are expected to be applicable to three-dimensional lattices as well. He provides an example calculation for a typical crystal structure, showing that dielectric breakdown is not expected until the electric field strength reaches around \(10^6\) volts per centimeter. The breakdown occurs suddenly as the field strength increases, with a significant increase in the transition rate. The paper concludes by summarizing the theory and its agreement with experimental findings, emphasizing that the transition between energy bands is negligible for field strengths obtainable in metals.The paper by Clarence Zener, titled "A Theory of the Electrical Breakdown of Solid Dielectrics," explores the mechanisms behind the sudden increase in current during dielectric breakdown in solid materials. The author begins by discussing the Bloch model of metallic conduction, where electrons move freely in a periodic lattice, and energy levels are grouped into bands. In insulators, these bands are fully occupied, but thermal excitation can introduce a few electrons into the upper, unfilled bands. The first mechanism for dielectric breakdown involves electrons being excited to higher energy levels by an external electric field, leading to an exponential increase in the number of electrons in the upper band. The second mechanism, which is the focus of this paper, involves the auto-ionization of free electrons in the presence of a strong electric field, similar to the auto-ionization of free atoms in gases. Zener uses the Bloch model to calculate the rate at which electrons transition from the lower to the upper energy bands under a constant electric field. He derives an expression for the probability of transition per unit time, which depends on the energy gap between the bands and the electric field strength. The theory predicts that dielectric breakdown occurs suddenly when the electric field reaches a critical value, consistent with experimental observations. The breakdown field magnitude and the suddenness of the breakdown are both explained by this second mechanism. In the discussion, Zener notes that the results obtained for a one-dimensional lattice are expected to be applicable to three-dimensional lattices as well. He provides an example calculation for a typical crystal structure, showing that dielectric breakdown is not expected until the electric field strength reaches around \(10^6\) volts per centimeter. The breakdown occurs suddenly as the field strength increases, with a significant increase in the transition rate. The paper concludes by summarizing the theory and its agreement with experimental findings, emphasizing that the transition between energy bands is negligible for field strengths obtainable in metals.