Journal zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of the Less-Common Metals, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIH 97(1984) 231- 236 231 zyxwvutsrq THE Th-In PHASE DIAGRAM A. PALENZONA, P. MANFRINETTI and S. CIRAFICI Zstituto di Chimica Fisica, Uniuersitd di Geneva, Corso Europa, Palazzo delle Scienze, 16132 Genoa (Zt a b) (Received June 20,1983) Summary The Th-In phase diagram was investigated using differential thermal analysis, X-ray diffraction examination and micrography. Four eutectics are formed at about 1.0 at.% Th, 31.5 at.% Th, 48.5 at.% Th and 74.0 at.% Th with characteristic temperatures of 155 “C, 1275 “C, 1265 “C and 1095 “C respectively. Four intermediate phases corresponding to the compositions Thin, (AuCu,- type structure), ThJn, (Pu,Pd,-type structure), Thin (ThIntype structure) and Th,In (CuAl,-type structure), were found. The equiatomic compound represents a new structure type. No appreciable solid solubility was found for any of the phases present or for thorium in indium, whereas up to 9.0 at.% In dissolves in thorium at 1095 “C. 1. Introduction The phase diagram of the Th-In binary system was investigated as part of a research programme which involves the revision of the crystallographic data for the thorium intermetallic compounds. The following phases have been reported in this system [l]: Thin, (AuCu,-type structure), Thin, (MgCu,-type structure) and Th,In (CuAl,-type structure). However, the phase diagram has been determined for only a limited range of compositions (O-33 at.% In [Z]). The crystal structures and lattice constants proposed for Thin, and Th,In appear to be consistent with a reasonable crystallochemical behaviour of thorium with indium, corresponding to volume contractions Av = Vcalc - Vobs x 1oo __ V talc during the formation of the compounds from the elements ranging from about 10.5% to 12.5%. However, for Thin, the proposed structure and particularly the volume contraction (AV = 52%) are unsatisfactory. For these reasons a com- plete reinvestigation of the phase diagram was undertaken. 002%5088/84/$3.00 c’ Elsevier Sequoia/Printed in The Netherlands