Electrical Properties of Crystallized Glasses in the System MgO‐Al ₂ O ₃ ‐SiO ₂ ‐TiO ₂

Abstract

The glass composition MgO 15.5, Al 2 O 3 19.5, SiO 2 58.5, and TiO 2 6.5 (wt%) was crystallized under controlled conditions in the range 900° to 1140°C and the electrical properties were studied. The activation energy for dc and ac conduction in the uncrystallized specimen was 32.0 and 27.4 kcal/mole, respectively; the corresponding values for the crystallized specimens were about 18.5 and 11.6 kcal/mole. X‐ray studies and color of the crystallized specimens suggested the presence of magnesium aluminum titanate crystals in which part of the titanium was reduced to the Ti 3+ state. These semiconducting phases were suggested as being responsible for the sharp change in the electrical properties and for the appearance of an apparent dielectric relaxation peak. Changes in the electrical properties with increasing crystallization temperature may be related to the nature, size, and shape of the crystals.