Thallium electrical resistivity

The mixed oxide ceramic Tl2Ca2Ba2Cu30io+x has zero electrical resistance at 125 K. Calculate the average oxidation number of the copper in this compound if x = 0.50 and thallium is in the -1-3 oxidation state. 

The Thalofide cell1 is more sensitive to light, especially that of low intensity and long wave lengths than the selenium cell. Its electric resistance drops 50 per cent on exposure to a quarter foot candle. The sensitive material contains thallium, oxygen, and sulfur and is essentially an oxysulfide of thallium. 

Other Thallium Compounds.— The electrical resistivities of K-Tl alloys over a wide range of compositions have been measured. The results suggest that a high degree of localized electron bonding occurs in the liquid alloy at a potassium mole fraction of 0.5. It is possible that the t)q)e of bonding is similar to that occurring in the solid intermetallic compound KTl, which crystallizes at lower temperatures. ... 

An interesting application of thallium is in superconducting materials. Superconductors have no resistance to the flow of electricity. Once an electrical current begins flowing in the material, it continues to flow forever. Thallium is also used in wireless communications. 

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