New oxychlorides, T-type CaRCuO3Cl (R=Y, Ho and Er), prepared under high pressure

We synthesized new copper-oxychlorides with the T^* structure CaRCuO₃Cl (R=Y, Ho and Er), using a high pressure technique. X-ray diffraction indicates that samples with nominal compositions of CaRCuO₃Cl (R=Y, Ho and Er) have a tetragonal structure with the a-axis lattice parameters in the range 3.84–3.86 Å, which are comparable to those of typical p-type superconductors. Both the a-axis and c-axis lattice parameters decrease approximately linearly with decreasing ion size R. The range cationic radius ratio of alkaline earth and rare earth elements for these copper-oxychlorides agrees with those previously reported for T^* copper-oxides and -oxychlorides.