A new phase of Ba2(Cu0.7Cd0.3)O3 has been discovered. The composition
of the phase was examined by energy dispersive X-ray spectrometry. The
phase exhibits a tetragonal structure with lattice constants a = 4.07
7 angstrom and c = 7.970 angstrom, and its space group is P4/mmm. We p
ropose a double-center-perovskite structure model, which is similar to
that of (Ba, Sr)2CuO2(CO3) [1,2]. The simulated XRD is close to the o
bserved one. The analysis results of elemental analyzer and Fourier tr
ansform infrared spectrometer reveal that the phase does not contain C
O3(2-). The cuprate is an insulator, but its new cell structure and th
e large size of the CuO2 planes seem to suggest a good reason for rese
arching new superconductors. The roles of CdO in the solid state react
ion and the formation of the new phase are discussed.