Single-crystal growth of Tl2Ru2O7 pyrochlore using high-pressure and flux method

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 B2O3 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 B2O3 flux proceeded at lower temperature by grain growth with material transfer through B2O3. The crystal obtained was characterized by single-crystal XRD method, and was found to have a stoichiometric composition, Tl2Ru2O7−δ (δ=0), with a structural phase transition around 120 K. The grain growth technique with B2O3 is efficient for high-temperature single-crystal growth under high pressure.