High field conduction and dielectric breakdown in nominally pure and nickel-doped MgO crystals at high temperatures

The phenomenon of dielectric (or more aptly, electrothermal) breakdown of nominally pure and nickel-doped MgO crystals at 1473 K is studied with the use of a field of 1500 V cm^-1. The current transients induced by constant and alternating fields as well as by field reversals, and open- and short-circuit conditions are investigated. Activation energies, obtained from the temperature dependence of current parameters, are also obtained. It is concluded that the mechanism leading to the breakdown involves the buildup of space charge caused by the injection of carriers from the electrodes and drift of ions.