ON THE SUPERCONDUCTING MECHANISM OF K3C60 AND Ba1-xKxBiO3

A superconducting mechanism for K₃C₆₀ and Ba_1-xK_xBiO₃ has been suggested. This is the combining picture of the Cooper pair and the Ogg pair. Numerical calculations within the framework of this picture have been done for K₃C₆₀ and Ba_1-xK_xBiO₃, and the overall consistency with the experimental data of superconducting properties is good.     

Self-consistent spatially inhomogeneous state in HTSC Ba1-x KxBiO3 single crystals

A spatially inhomogeneous state in HTSC Ba_1-x K_xBiO₃ single crystals (T _c ≈ 30 K, x = 0.4) has been studied at T < ? ≈ 17 K, where ? is the temperature of separation into superconducting and dielectric phases. This separation has earlier been detected in Ba_1-x K_xBiO₃ polycrystals. In the single crystals, the main results are obtained from hysteretic magnetization reversal curves, whereas the character of separation in the polycrystals is clearly visible from I–V curves. The results obtained support the theoretical model of HTSC separation proposed in [1].     

Some dielectric properties of Ba1-xSrxTiO3 single crystals grown from a KF flux

The temperature dependences of permittivity and of hysteresis loops in the range of 4.2 K to 600 K were measured on mixed Ba_1-xSr_xTiO₃ single crystals, grown in the whole concentration region 0≦x≦1 from a KF flux. It is shown that a solid solution with dielectric properties compatible with existing theories is formed by isovalent substitution of Ba by Sr only for x=0?0.4 and 0.8?1. A comparison between our results on single crystals and previous measurements on mixed ceramic materials is carried out.