Thermochemistry of some Zinc-Transition metal(TM) compounds and some Bismuth-TM compounds by high temperature direct synthesis calorimetry

Abstract

Intermetallic compounds such as Heusler and half-Heusler alloys have a number of interesting properties and are being developed for numerous applications. Such alloy development requires thermodynamic data and our work is aimed at providing such data to the scientific community.The standard enthalpies of formation of some zinc, bismuth and transition metal(TM) compounds have been measured by high temperature direct synthesis calorimetry at 1273 ± 2 K. The following values for the TM-Zn compounds are reported in kJ/mole of atoms:ScZn (-41.4 ± 3.0); PdZn (-37.0 ± 3.0); Hf2Zn (-9.8 ± 2.3); PtZn (-24.8 ± 2.5).Bismuth yields approximately 15–20 binary transition metal compounds and 12–20 binary compounds with lanthanide elements. Some of these compounds have semiconductor properties and as such could be potentially useful for industrial endeavors, which is particularly noted for PdBi, RhBi, HfBi and ZrBi.The standard enthalpies of formation of some Bi-TM compounds have been measured by high temperature direct synthesis calorimetry at 1273 ± 2 K. The following values are reported in kJ/mole of atoms; Ti2Bi (-15.2 ± 3.2); Y5Bi3 (-81.7 ± 2.5); ZrBi (-47.3 ± 3.1); BiRh (-17.2 ± 2.8);PdBi (-30.2 ± 3.1); BiPt (-17.8 ± 2.9). All the measurements refer to 298 K.The results for both the TM-Zn and the TM-Bi compounds are compared with available thermodynamic data from the published literature and with predicted values from both Miedema's semi-empirical model and from ab initio calculations.