Effect of boron substitution on the crystallographic structure and superconducting properties in Y_(1-x)B_xBa_2Cu_3Oy system

摘要

The changes in crystallographic and transport properties in the polycrystalline Y_(1-x)B_xBa2Cu_3Oy (YBBaCuO) compounds with x ranging from 0 to 0.55 have been investigated. Samples were synthesized using standard solid state reaction technique. The structure for all samples was characterized by X-ray diffraction with Rietveld refinements technique. Their transport properties were measured by the standard four probe method in the temperature range from 20 to 300 K. The crystal lattice parameters are found to change due to the boron doping and YBBaCuO samples undergo to a structural phase transition from orthorhombic to tetragonal at x of more than 0.3. With the increase of x the transition temperature (Tc~(onset)) decreases. The dependence of resistivity on temperature, and the relation of the structural parameters versus the content of boron are discussed.