Flux growth and physical properties of pyrochlore Pb2Ru2O6.5 single crystals

Cubic pyrochlore Pb2Ru2O6.50+/-0.02 single crystals were grown from a PbO flux by a slow-cooling method under ambient atmosphere. The obtained crystals were black and formed quasi-cubes and cuboctahedra. The largest crystal with a size up to 9 x 7 x 4 mm(3) was grown from the mixture of RuO2 and PbO with a molar ratio RuO2/PbO = 1/9, which was heated to 1250 degreesC, held for 10 h, and then cooled at a constant rate of 5.0 degreesC/h to 950 degreesC. It was found that the vaporization of PbO is important for crystal growth. The electronic resistivities for the crystal were 2.3 x 10(-4) Omegacm at 300 K and 2.0 x 10(-6) Omegacm at 2K, respectively. The temperature dependence of the resistivity indicates that this compound is metallic and the DC magnetic susceptibility reflects the delocalized character for electrons of Ru. (C) 2004 Elsevier B.V. All rights reserved.