Crystallinity and transport properties in Bi_2Sr_2Ca_(1-x)Pr_xCu_2O_y single crystals

摘要

Bi_2Sr_2Ca_(1-x)Pr_xCu_2O_y (x ranging from 0 to 0.5) single crystals have been grown by a self-flux method from Bi-rich melts. The crystals obtained manifest slim and plate-like shapes. The crystallinity is studied by x-ray diffraction. The x-ray #theta#-scanning rocking curve shows that the slim crystal has perfect crystal structure while the plate-like crystal is mosaic dong the c-axis. The in-plane resistivity #rho#_(ab)(T) has been measured for crystals with different Pr doping levels. T_c is suppressed gradually upon doping while the residual resistivity increases strongly. A superconductor-insulator transition is observed which is attributed to lie tetragonal-orthorhombic phase transition when the Pr content reaches about 0.5. The effect of oxygen doping on in-plane resistivity #rho#_(ab)(T) is also studied for x = 0.22 and 0.40 stals.