Abstract
Recently, ceramic bodies containing talc or other magnesium silicates have been called much attention in the field of the electrical insulation owing to their low dielectric loss and high insulation resistance at high temperatures. The electrical resistance of Manchuria talc-Kato kaolin system was determined. The results can be expressed by the equation logρ=B+A/T°K, where ρ is the resistivity in MΩ.
The relation of the resistivity at 400°C with the composition of the bodies is represented by
logρ(400°C)=-0.0296k+4
where k is the percentage of Kato kaolin in the fired bodies.
Kato-kaolin contains 0.85% alkalies in the anhydrous state and according to the previous investigation (S. Moriyasu, J. Jap. Cer. Assoc., 1936, 44 (528), 856), the resistivity of the system Al2O3SiO2 is very much influenced by the presence of alkalies. On the absence of alkalies, the resistivity of 3MgO⋅4SiO2-Al2O3⋅2SiO2 system should be approximately represened by
logρ(400°C)≅-ak+4
where the coefficient a is probably 0.01 or less.
A simple method of the determination of the resistivity less than 100MΩ (at 400°C) was described. (Elec. Tech. Laboratory, Ministry of Communication, Tokyo.)
