RIETVELD ANALYSIS AND SUPERCONDUCTIVITY OF LA1.5CAXBA1.5-XCU3OY COMPOUNDS

A series of single phase La1.5CaxBa1.5-xCu3Oy (0 less than or equal to x less than or equal to 0.50) compounds with tetragonal triple-perovs kite structure is studied by Rietveld analysis. For x less than or equ al to 0.40, all the Ca2+ ions enter the center site, the Y3+ site of t he tetragonal YBa2Cu3Oy phase. For x = 0.50, occupation factor of Ca2 ion in the Y3+ Site (OFCa/Y) is 0.466(2). The maximum allowed OFCa/Y is close to 0.50 which limits further substitution of Ca2+ ion to the Ba2+ ion for the La1.5CaxBa1.5-xCu3Oy series. T-c can be explained by the difference between OFCa/Y and OFLa/Ba, (OF of La3+ ion in the Ba2 site). In other words, superconductivity is determined by the amount of Ca2+ ions in the Y3+ Site and La3+ ions in the Ba2+ site in the uni t-cell.