Remarks on the role of thermochemical data in intermetallic crystallochemistry

It is well known that a sound investigation of intermetallic systems is based on a concerted experimental approach using several complementary techniques. The identification and characterization of an intermetallic phase in principle requires the determination of its crystal structure and some information about its stability, possibly as a function of temperature and composition. Very often, therefore, phase identification and phase equilibria are studied at the same time. Both types of investigation (which are strictly interconnected) are important for a complete characterization of the phase. In this activity, and in the subsequent assessment and optimisation procedures, thermodynamic data are necessary. These data and their measurements may be subdivided into two main categories: that concerning properties of single phases (heat capacity, heat of melting, etc.) and that including reactions (for instance formation of the phase). In this paper attention is mainly focused on the activity carried out in the authors' laboratory, especially dedicated to the determination of thermodynamic functions of formation. Several instruments constructed in the laboratory are described and a summary of the alloy systems studied is given. (C) 2003 Elsevier B.V. All rights reserved.