Thermochemical investigations in the system Cd-Gd

Area of Science:

• Materials Science
• Thermodynamics
• Physical Chemistry

Background:

• Understanding the thermodynamic properties of intermetallic compounds is crucial for materials development.
• The Cadmium-Gadolinium (Cd-Gd) system is of interest for its potential intermetallic phases.

Purpose of the Study:

• To determine the thermodynamic activities of Cadmium (Cd) in Cd-Gd alloys.
• To calculate partial molar enthalpies and integral Gibbs energies of mixing.
• To assess the stability of intermetallic phases in the Cd-Gd system.

Main Methods:

• Non-isothermal isopiestic method for vapor pressure measurements.
• Gibbs-Helmholtz equation for calculating partial molar enthalpies.
• Gibbs-Duhem integration for determining integral Gibbs energies.

Main Results:

• Thermodynamic activities of Cd were derived across various compositions and temperatures (693-1045 K).
• Partial molar enthalpies of mixing for Cd were obtained and used to normalize activity values to 773 K.
• Integral Gibbs energies and Gibbs energies of formation for specific Cd-Gd phases were calculated at 773 K.

Conclusions:

• The intermetallic phases Cd2Gd and Cd45Gd11 exhibit significant stability within the Cd-Gd system.
• Gibbs energies of formation at 773 K range from approximately -19.9 to -30.0 kJ/g atom for studied phases.