NEW QUADRUPLE PEROVSKITES LN2BA2TIXSN2-XCU2O11, 0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-2) - CONTROLLING COPPER-OXYGEN DISTANCES INPOTENTIAL SUPERCONDUCTING PARENT PHASES

The compounds Nd2Ba2Cu2SnTiO11, Sm2Ba2Cu2Sn0.5Ti1.5O11 and Gd2Ba2Cu2Ti 2O11, have been synthesized by reaction of the component oxides at 102 5-degrees-C and their structures refined from powder X-ray diffraction data. The materials crystallise with a quadrupled perovskite unit cel l, similar to that of La2Ba2Cu2Sn2O11 containing alternating double la yers of copper and titanium/tin. Decreasing lanthanide size and increa sing titanium content is associated with a marked unit cell contractio n and a reduction in the mismatch between the different double-layer d imensions. A reduction in the copper-oxygen distances in the CuO2 plan es from 2.007 angstrom in La2Ba2Cu2Sn2O11 to 1.951 angstrom in Gd2Ba2C u2Ti2O11 produces a copper-oxygen interaction similar to that found in high-temperature superconductors.