Ceramic semiconductor SnO₂-based materials with MnO₂ and CuO additives were synthesized at 1300 ºС and 1400 ºС. There has been carried out an investigation of the physical–mechanical and high–temperature electric properties. As a result, sintering of the material with MnO₂ additive is shown to be improved at increasing firing temperature. The composition 96%SnO₂-2%Sb₂O₃-2%CuO made at the temperature 1300 ºС has the best electrophysical properties (its resistivity is 0.09 mOhm m). The resistivity of the 94%SnO₂-2%Sb₂O₃-2%CuO-2%MnO₂ composition in the high-temperature region is more by a factor of 3. The 96%SnO₂-2%Sb₂O₃-2%MnO₂ composition has nonlinear voltage-currant characteristic, and hysteresis is present.