Synthesis, Crystal Structure and Magnetic Properties of Ba2Cu2WYO8.5-δ

Polycrystalline Ba2Cu2WYO8.5-δ has been synthesized by calcination at 1160°C. It crystallizes in the cubic system with the space group F43̄m, a=8.345 Å and Z=8/3. The structure consists of a superstructure of the perovskite type, whose three main axes are doubled. Thus, the structure is well illustrated if the formula is written as [ACuO3-ε][A(W2/3Cu1/3)O3-ε] with A=Ba or (Y2/3Ba1/3) and 1/6<ε<1/2. The existence of Cu+ was confirmed from the measurement of magnetic susceptibility. Unlike YBa2Cu3O6.5+δ, the substance exhibits no superconductive behavior even after 12 hours of heat treatment in O2 at 450°C.