Bi₂(Sr_1-xCa_x)₂(Ca_1-yY_y)Cu₂O_δ の合成と超伝導転移

抄録

Single phase Bi₂(Sr_1-xCa_x)₂(Ca_1-yY_y)Cu₂O_δ is successfully prepared in the range of 0≤x≤0.8 and 0≤y≤0.6 by a solid state reaction in air. The optimal sintering temperature for forming the single phase is reduced from 875°C to 800°C with substitution of Y in the Ca site or with increased Ca in the Sr site. The lattice parameter c reduced from 3.081 to 3.017 nm by substituting Ca with Y and/or Sr with Ca. Bi₂(Sr_1.0Ca_0.0)₂(Ca_0.8Y_0.2)Cu₂O_δ, is superconducting after heat treatment either in Ar or O₂ while the phases Bi₂(Sr_0.6Ca_0.4)₂(Ca_0.8Y_0.2)Cu₂O_δ, Bi₂(Sr_1.0Ca_0.0)₂(Ca_0.4Y_0.6)Cu₂O_δ and Bi₂(Sr_0.4Ca_0.6)₂(Ca_0.4Y_0.6)Cu₂O_δ are superconducting only after oxygenation. The oxygen stability and optimum heat treatment temperature for superconductivity depend on the Sr/Ca and Ca/Y ratios in Bi₂(Sr_1-xCa_x)₂(Ca_1-yY_y)Cu₂O_δ.