Thermal cnductivity and Lorenz number of plutonium and plutonium-gallium alloys

The thermal diffusivities of Pu, Pu-2.7 at. % Ga, Pu-3.5 at. % Ga, and Pu-6.6 at. % Ga were measured from 250C to around 5000C using a laser flash technique and electronic data acquisition. Although the Lorenz number, L, of pure Pu is well below the Sommerfeld value, L0, except for the α-phase, L exceeds L0 for the alloys at all temperatures and has a pronounced minimum around 2000C. At the lower temperatures we attribute the excess to lattice conduction and at temperature above 2000C the excess is attributed to an electronic component. The negative deviation of L from L0 for pure Pu is ascribed to a reduction of the electron mobilities in those energy ranges where the 5f bands overlap the conduction bands