Electrical conductivity and enthalpies of transformation in Li2UBr6 between 500 and 800 K

As with Na2UBr6, previously investigated, Li2UBr6 undergoes several transitions before melting. These were studied using electrical-conductivity measurements, differential thermal analysis and differential enthalpic analysis performed in the temperature range 500 to 800 K. For Li2UBr6 the thermal effects before fusion are insignificant and are much smaller than those found for Na2UBr6, while the enthalpy of fusion is larger. For both compounds, comparable values were found by summing the entropies of transformation. Results are presented. The variation of electrical conductivity with temperature is very different for these compounds. While continuous evolution is observed for Li2UBr6, each transition of Na2UBr6 corresponds to a jump in conductivity. The results obtained for Li2UBr6 are discussed by comparison with those previously obtained for Na2UBr6. (author)