Actinide phase homogeneity

Characterization. Actinide metal samples for the determination of properties related to bonding have to be characterized for chemical purity and phase homogeneity. Purity is checked by chemical or physical analysis, crystal structure is determined by X-ray or neutron diffraction techniques phase heterogeneities can be observed by metallography. 

Typically, binary Laves compounds AM2 are formed in several systems of A metals such as alkaline earths, rare earths, actinides, Ti, Zr, Hf, etc., with M = Al, Mg, VIII group metals, etc. Laves phases are formed also in several ternary systems either as solid solution fields extending from one binary phase (or possibly connecting the binary phases of two boundary systems) or as true ternary phases, that is forming homogeneity fields not connected with the boundary systems. 

Several ternary phases are known, often homogeneous in more or less large ranges of compositions formulae such as —MeAlgTg, —MeAl8T4 (Me = lanthanides, actinides, T = Mn, Cr, Fe) are frequently found and also several isostruc-tural phases with Ga instead of Al. According to the systematic presentation and classification of intermetallic phases presented by Parthe and Chabot (1984), some... 

ThP(cr) has the fee NaCl stracture, isomorphous with most of the lower actinide MX(cr) compounds, (X = N, S, P). It was initially thought to have a considerable range of homogeneity [1965GIN/WIL], but in a detailed study of the Th-ThP subsystem, Javorsky and Benz [1967JAV/BEN] showed that the lower phase boundary is at ca. ThPo.98 over most of its range of stability. The upper phase boimdaiy has still not been established. 

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