Critical crystal-chemical parameters controlling T-c of HTSC cuprates

For all high-temperature superconductive (HTSC) cuprate phases, an empirica l relationship has been found between the temperature of the transition to the superconducting state (T-c) and the ratio between the interatomic dista nces of copper atoms along the diagonal of the CuO2 plane and the sum of "e ffective" distances from the CuO2 plane to two adjacent cation planes calcu lated with regard to the charge and size of the cations and doping atoms. T he critical parameters controlling T-c are discussed.