Abstract The new oxide Ba 2 NdZrO 5.5 (BNZO) has been produced by the standard solid state reaction method. X‐ray diffraction analysis (XRD) revealed that this synthesized material has an ordered complex cubic perovskite structure characteristic of A 2 BB'O 6 crystalline structure with a lattice parameter of a = 8.40 Å. It was established through EDX analysis that there is no trace of impurities. Chemical stability of BNZO with YBa 2 Cu 3 O 7‐δ (YBCO) has been studied by means of Rietveld analysis of experimental XRD data on several samples of BNZO‐YBCO composites. Quantitative analysis of phases on XRD patterns show that all peaks have been indexed for both BNZO and YBCO, and no extra peak is detectable. YBCO and BNZO remain as two different separate phases in the composites with no chemical reaction. Electrical measurements also revealed that superconducting transition temperature of pure YBCO and BNZO‐YBCO composites is 90 K. These favorable characteristics of BNZO show that it can be used as a potential substrate material for deposition of YBCO superconducting films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)