Material preparation and superconducting properties of Li-Pd-B ternary boride

A superconducting material of Li2Pd3B with the superconducting transition temperature (Tc) at 8 K was recently discovered. This material has a cubic structure with a lattice parameter a = 0.675 nm and a P4332 symmetry composed of distorted 6Pd octahedrons centered by B. We have tried several methods to prepare the samples by arc-melting, radio-frequency heating and heat treatment in Ta tube. The loss of Li was evaluated by chemical analysis to synthesize the stoichiometric Li2Pd3B. Low-temperature X-ray powder diffraction down to Tc was performed. Shrinking of the lattice parameters with a decrease in the temperature was observed, but no structural transformation occurred between 7.6 K, just below Tc, and room temperature. The upper critical field Hc2(0) was 62 kOe determined by the measurement of electrical resistance under up to 50 kOe. The heat capacity and magnetization were also measured and their data proved the bulk superconductivity in Li2Pd3B.