Structural and oxygen stoichiometric studies on La1.5-x Cax+y Ba1.5-y Cu3Oz system

The superconducting properties of single phase La1.5-xCax+yBa1.5-yCu3O2, 0.0 less than or equal to x less than or equal to 0.5, y = 0.0 (LC-series) and x = 0.5,0.0 I y I 0.5 (CB-series) compounds are found to depend on the changes in Ca-concentration which helps to increase the additional oxygens in the stable tetragonal structure resulting into the creation of holes thereby preserving the charge balance. In the present study we report the mechanism to alter the hole concentration in the planes by substituting divalent Ca at trivalent La and Ba sites which helps to induce the superconductivity (up to 75K) in the non superconducting (NS) tetragonal La1.5Ba1.5Cu3Oz(x = y = 0.0). Our results are discussed in the context of variation of lattice parameters, oxygen stoichiometry (z) and hole concentration (p) in the tetragonal La-Ca-Ba-Cu-O system.