Single-crystal growth of Tl 2Ru 2O 7 pyrochlore using high-pressure and flux method

Abstract

Single crystals of the thallium ruthenium pyrochlore have been grown by flux method under high oxygen pressure. The growth conditions were determined by direct observations using in situ powder X-ray diffraction (XRD) method under high pressure and high temperature. The crystals were grown using NaCl–KCl flux at 1350 °C and B 2O 3 flux at 1150 °C. High growth temperature of 1350 °C for the NaCl–KCl flux caused Pt contamination from the crucible and oxygen deficiency for the crystals obtained. The crystal growth using B 2O 3 flux proceeded at lower temperature by grain growth with material transfer through B 2O 3. The crystal obtained was characterized by single-crystal XRD method, and was found to have a stoichiometric composition, Tl 2Ru 2O 7− δ ( δ=0), with a structural phase transition around 120 K. The grain growth technique with B 2O 3 is efficient for high-temperature single-crystal growth under high pressure.