Stabilization of a superconducting TbSr<inf>2</inf>Cu<inf>2.85</inf>Re <inf>0.15</inf>O<inf>7+δ</inf> compound and the valence state of terbium

A single-phase Sr-based Tb-123 phase has been synthesized by chemical stabilization. TbSr2Cu2.85Re0.15O 7+δ exhibits superconductivity at Tc,zero=22 K. X-ray diffraction results suggest a relatively small orthorhombicity and neutron diffraction studies indicate an excess oxygen content (≥7.2) in the sample. Tb is present as a trivalent ion in the superconducting phase as derived from x-ray photoelectron spectroscopy.© 1995 American Institute of Physics.