The structure-property relationships of the chemically substituted quadruple and quintuple perovskites, NdDyBa2-xSrxCu2+yTi2-yO11 and NdDyCaBa2-xSrxCu2+yTi2-yO14, were investigated with regard to the high-temperature electrical properties. The substitution of Cu for Ti in both systems, especially the quadruple system, improved the electrical properties. Substantial compensation by O vacancies occurred. On the other hand, isovalent Sr substitution of Ba in these systems significantly reduced the ionic compensation. That is, it reduced the [VO] concentration; as shown by thermogravimetric and electrical measurements. The substitution of Sr not only reduced the Cu-O bond length in favor of hole formation, but also introduced metallic behavior as reflected by in situ high-temperature (400-800C) electrical conductivity and Seebeck-coefficient measurements, as well as low-temperature resistivity measurements.

Quadruple and Quintuple Perovskite-Layered Cuprates - their Defect Chemistry and Electrical Properties. N.Mansourian-Piadavi, D.Ko, T.O.Mason, K.R.Pöppelmeier: Journal of Solid State Chemistry, 2000, 155[1], 216-24