Synthesis, Thermal Stability, Structural Features and Electromagnetic Properties of Bi2+x Sr2-x CuO6+d (0￡x￡0.4) (SOLID STATE CHEMISTRY-Quantum Spin Fluids)

Abstract

The thermal stability and structural modulation were studied systematically in a wide range of 0 ￡ x ￡ 0.4 for the 2201 phase in the Bi-Sr-Cu-O system, Bi2+xSr2-xCuO6+d, and it was found that these properties varied remarkably at x ≫ 0.1. Compositions 0 ￡ x < 0.1 remained stable only in a narrow low T- high Po2 region and their modulation period changed stepwisely, not continuously, and reversibly between 4.9b (oxidized) and 5.5b (reduced) when the oxygen content was changed only by 0.65%. In relation to this we propose for 0 ￡ x < 0.1 specifically that the change in oxygen content induces the exchange of small amounts of Bi and Sr ions between the "BiO" and "SrO" sheets. The superconductivity of the cation-stoichiometric composition (x = 0) was also studied as a function of oxygen content.