J. Paul Attfield and colleagues from the University of Edinburgh have shown that using high pressure could double the number of a new group of high temperature superconductors.
Motivated by the discovery of superconductivity in the first half of the rare earth series (F-doped RFeAsO with R = La-Gd), they decided to investigate whether it was possible to stabilise doped-RFeAsO superconductors from the second half of the series, with R = Tb-Lu.
Using high pressure synthesis, Attfield and colleagues successfully synthesised F-doped TbFeAsO and DyFeAsO superconductors, with critical temperatures of 46 and 45 K respectively.
Attfield believes that this new group of superconductors is the most important discovery in this field since the high-Tc cuprate materials were found 20 years ago. He plans to also stabilise later rare-earth superconductors using the higher pressures. 'The chemical challenges are considerable - preparing phase pure samples of quaternary compounds under high pressure and temperature conditions is time consuming, and the structural and physical characterisation of the small (~20 mg) samples is also demanding. Higher pressures which are likely to be needed for the smallest rare-earths place more stress on the synthesis module, and further reduce the sample size.'
Original publication: J. Paul Attfield et al., Chem. Commun., 2008