Superconductivity with transition temperature up to 80 K for TbSr2Cu2.7Mo0.3O7+δ

A Tb-123 phase with the composition, TbSr 2 Cu 2.7 Mo 0.3 O 7+ δ , has been synthesized in single-phase form by the solid-state reaction route. Its phase purity has been confirmed from neutron powder diffraction studies. The as-synthesized Tb-123 sample does not show superconductivity down to 5 K. On the other hand, an unusually high antiferromagnetic ordering temperature ( T N ) of around 7 K is seen for the Tb moments. After 120-atm-O 2 post-annealing, bulk superconductivity is achieved in this compound with a superconducting transition temperature ( T c ) of about 30 K, without any significant effect on T N . To achieve higher oxygen content and higher T c , the as-synthesized sample was subjected to high-pressure oxygenation, carried out in a closed cell, at 5 GPa and 400 °C in the presence of AgO as an excess-oxygen source. This sample exhibited superconductivity onset at around 80 K with a Meissner fraction larger than 10% at 5 K. Our observation of superconductivity at 80 K is the highest T c to-date for the Tb-123 type compounds.