Electric Breakdown in MgO Crystals at Elevated Temperature

Experiments are performed to determine the source of the increase in conductivity and consequent breakdown of MgO subject to moderate electric fields. Results are reported on the effect of the presence of impurities and metallic precipitates on the rate of current increase and on the defect microstructure observed by transmission electron microscopy. Experiments involving reversal of the polarity of the electric field are performed, and electron-paramagnetic-resonance spectra resulting from electric field treatment are described. The results are discussed in terms of stable metallic pathways, thermal emission of current carriers from colloids, and changes in the distribution of defects and impurities.