Electrical Resistance of Some Refractory Oxides and Their Mixtures in the Temperature Range 600° to 1500°C.

Measurements of electrical resistance in the composition systems Al 2 O 3 –SiO 2 , SiO 2 –TiO 2 , Al 2 O 3 –Cr 2 O 3 , and MgO–NiO were made using, in general, dry‐pressed disks about 3 cm. in diameter and 0.4 cm. thick and fired to 1500°C. In the Al 2 O 3 –SiO 2 series minimum resistance was shown by the samples containing 50% SiO 2 , 50% Al 2 O 3 . The resistance of Al 2 O 3 was increased by the addition of small amounts of Cr 2 O 3 . The same effect was observed in the higher temperature range with small additions of NiO to MgO. In other instances the addition of the relatively inert SiO 2 , Al 2 O 3 , and MgO to the semiconductors TiO 2 , Cr 2 O 3 , and NiO resulted in a dilution effect. The resistance of Cr 2 O 3 was decreased by the addition of a slight amount of MgO.