Abstract
Samples of Bi1.7Pb0.3Sr2Ca2Cu3O10+y (2223) annealed in different atmospheres and having different value of Tc and oxygen contents were obtained and examined by a wide range of measurements as well as theoretical calculation. A roughly quantitative relationship among Tc, oxygen content, c direction thermal expansion coefficient, and mismatch factors are established. It is revealed that the mismatch is important for superconductivity.