Speaker
Ms
Margarida Henriques
(Departamento de Química, Instituto Tecnológico e Nuclear/CFMC-UL, 2863-953 Sacavém, Portugal)
Description
Investigations on uranium-based ternary intermetallics continue to reveal new phases, with specific structures and rich variety of ground-state properties. In the U-Fe-Ge system the previously reported ternary intermetallic compounds were UFeGe (P21/m, type UFeGe below 500K, and Pnma, type TiNiSi above 500K) [1], UFe2Ge2 (I4/mmm, type ThCr2Si2) [2], UFe6Ge6 (P6/mmm, type YbCo6Ge6) [3], and the solid solution U2Fe17-xGex with 2<x<3 (P63/mmc, type Th2Ni17) [4], in addition to the recently reported U2Fe3Ge compound (P63/mmc, type MgZn2) [5, 6].
Following the previous work made on the U-Fe-Ge system [7], the aim of the present study is to complete the experimental investigation of the 900ºC isothermal section of the U-Fe-Ge phase diagram and the characterization of the new intermetallic compounds.
The samples were prepared by direct melting the calculated amounts of U, Fe and Ge elements (purity >99.9 mass%), in an arc-melting furnace and under high purity argon atmosphere, followed by annealing at 900ºC for one week inside evacuated quartz ampoules. The microstructure of all samples was analysed by SEM-EDS and the crystalline structure was characterized by powder and single-crystal X-ray diffraction.
The existence and composition of all the binary phases previously reported at 900ºC were confirmed and their crystal data are in agreement with literature. The binary compound UFe2 is the only one existing in the U-Fe system at the studied temperature, and in this ternary system, there is a substitution of iron by germanium in an amount up to 6.7 at%, as solid solution UFe2-xGex. All the other binary phases have negligible solubility extensions into the ternary system at this temperature.
The isothermal section was found to be very rich: there are 13 stable phases at 900ºC. Among these, there are nine new intermetallic compounds: U34Fe4-xGe33, UFe1-xGe2, U3Fe2Ge7, U9Fe7Ge24, U2Fe3Ge, U6Fe16Ge7, U3Fe4Ge4, UFe4Ge2 and U6Fe22Ge13. Within these new phases, three are new original structural types: U34Fe4-xGe33 and U9Fe7Ge24 (tetragonal system), and U6Fe22Ge13 (orthorhombic system). Within this section there are also two solid solutions UFe6+xGe6-x (x<0.7), which crystallizes in the YCo6Ge6 structure type and U2Fe17-xGex (with 2<x<3.7), crystallizing in the Th2Ni17-type structure [7].
Author
Ms
Margarida Henriques
(Departamento de Química, Instituto Tecnológico e Nuclear/CFMC-UL, 2863-953 Sacavém, Portugal)
Co-authors
Mr
Adrien Lignie
(Sciences Chimiques de Rennes, Laboratoire de Chimie du Solide et Matériaux, UMR CNRS 6226, Université de Rennes 1, Rennes, France)
Prof.
Alberto C. Ferro
(Departamento Engenharia Materiais, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal)
Dr
António P. Gonçalves
(Departamento de Química, Instituto Tecnológico e Nuclear/CFMC-UL, 2863-953 Sacavém, Portugal)
Dr
David Berthebaud
(Sciences Chimiques de Rennes, Laboratoire de Chimie du Solide et Matériaux, UMR CNRS 6226, Université de Rennes 1, Rennes, France)
Dr
Henri Noel
(Sciences Chimiques de Rennes, Laboratoire de Chimie du Solide et Matériaux, UMR CNRS 6226, Université de Rennes 1, Rennes, France)
Prof.
Olivier Tougait
(Sciences Chimiques de Rennes, Laboratoire de Chimie du Solide et Matériaux, UMR CNRS 6226, Université de Rennes 1, Rennes, France)
