High-temperature electrical property and defect analysis of the quintuple perovskite layered cuprates Eu2CaBa2Cu2Ti3O14 and LaYCaBa2Cu2+xTi3-xO14-y

High-temperature electrical conductivity and thermopower measurements have been performed on undoped Eu2CaBa2 Cu2Ti3O14 and doped and undoped LaYCaBa2 Cu2+xTi3-xO14. These quintuple perovskites are members of a family of order ed perovskite-type oxides with double Cu-O sheets and have inplane Cu-O bon d lengths comparable to known superconductors. X-ray diffraction data and t ransmission electron microscopy show clear evidence of layering in both str uctures. LaYCaBa2 Cu2+xTi3-xO14 exhibits a large-small rare earth ordering on the A'/A " sites, like its quadruple perovskite counterparts. The transp ort data indicate that these materials behave similarly to the correspondin g quadruple perovskites, but have lower carrier concentrations. The La-Y co mpound exhibits weaker oxygen partial pressure dependencies in the electric al properties, which are suggestive of a decrease in undesirable oxygen int ercalation between the CuO2 sheets. Upon doping with copper on titanium sit es, (Cu-Ti"), a concomitant amount of oxygen vacancies, (V-o(..)), are intr oduced, as evidenced by TGA and in situ electrical property measurements. P ossible defect models are presented and discussed in light of data from TGA , electrical property measurements, and quantitative high-resolution TEM, ( C) 1999 Academic Press.