Effects on structure and superconductivity for La and Ca codoping in YBa2Cu3Oy cuprates

The nominal composition of Y0.8Ca0.2Ba2-xLaxCu3Oy (YBLCO) cuprates with x l ess than or equal to 0.50 has been synthesized by the standard solid state reaction technique. X-ray diffraction and the resistivity measurements are used to characterize the structure and the superconductivity of YBLCO cupra tes. There is no structural phase transition in the whole doping range. The dependencies of the lattice constants and some other structural parameters on the content of La for the samples YBLCO with x less than or equal to 0. 20 are different than those for the samples with x greater than or equal to 0.25. The zero resistance temperature T-c0 increases with the increase of the content of La in YBLCO as x less than or equal to 0.20, and decreases a s x greater than or equal to 0.25. We compared these results with those of Nd-doped Y0.8Ca0.2Ba2-zNdzCu3Oy cuprates. It seems that T-c0 is related to the structural parameters due to Ca and La codoping in YBLCO. (C) 1999 Else vier Science B.V. All rights reserved.