Influence of an electric field on the plastic deformation of fine-grained MgO at high homologous temperatures

Abstract The effect of a dc electric field up to 385 V/cm on the stress–strain behavior in tension of fine-grained MgO (do=5.3 μm) was determined at 1500–1600°C. The field produced a decrease in the flow stress and an increase in the elongation. The reduction in flow stress was reversible and proportional to the field strength, amounting to ∼50% of the flow stress for E=220 V/cm. The field had only little, if any, influence on the stress exponent n=∂ ln e /∂ ln σ , which had a value of ∼1.0, indicating that it did not change the rate-controlling mechanism. The decrease in flow stress produced by the field is given by Δσ ∗ E =Z e Ex sc /Ω where Z=+2 is the charge on the rate-controlling Mg2+ ions, e is the electron charge, E is the field strength, xsc is the width of the space charge region and Ω is the atomic volume. The present results are the first of their kind which provide experimental support for the use of an electrochemical potential in diffusion flux equations pertaining to the plastic deformation of ceramic materials.