Effect of Microstructure on Pulse Electrical Strength of MgO

Pulse electrical strengths of hot-pressed MgO containing 0.3 wt% LiF were measured. Strengths as high as 5.9×10⁸ V/in. were obtained on samples 99.8% of theoretical density with 1-to 3-μm grain size. An increase of either porosity or grain size resulted in a monotonic decrease in strength. Single-crystal strengths of 4.0×10⁶ V/in. were obtained by polishing samples chemically. A simple recessed-electrode configuration eliminated corona effects.