Synthesis and characterization of La4BaCu5O13+δ and La4BaCu5-xMxO13+δ: M=Fe, Co, Ni, Zn

La4BaCu5-xMxO13+δ: M=Fe, Co, Ni, Zn were prepared by the solid-state route at 1000 deg. C. Solid solution limits of x=1.0(1) [Fe], x=1.1(1) [Co], x=1.56(7) [Ni] and x=0.47(1) [Zn] were determined from XRD and EPMA results. Rietveld refinement of combined XRD/neutron powder diffraction data was carried out on undoped La4BaCu5O13+δ and x=1 for M=Fe, Co, Ni. For La4BaCu5O13+δ, which is an oxygen-deficient perovskite, the presence of square planar CuO4 groups, disordered over the Cu(2) sites with CuO5 square pyramids, is indicated, together with, for δ<0, either square planar CuO4 or square pyramidal CuO5 and octahedral CuO6 groups disordered over the Cu(1) sites. For M=Fe, Ni, there was preferential substitution onto the one-fold octahedral site; for M=Co, substitution took place on both the one-fold octahedral and four-fold square pyramidal sites