Suppression of binary nucleation in amorphous La-Fe-Sb mixtures

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Skutterudite compounds, such as La(x)Fe(4)Sb(12), are of interest for thermoelectric applications.
• Controlling the nucleation and growth of these complex materials is crucial for optimizing their properties.
• The influence of reactant composition on nucleation pathways is not fully understood.

Purpose of the Study:

• To investigate the nucleation energy of La(x)Fe(y)Sb(z) modulated elemental reactants.
• To determine the effect of the Fe/Sb ratio on the nucleation of the ternary skutterudite compound La(0.5)Fe(4)Sb(12).
• To understand the role of lanthanum in suppressing binary phase nucleation.

Main Methods:

• Measurement of nucleation energy for La(x)Fe(y)Sb(z) reactants across a range of Fe/Sb ratios.
• Comparison of nucleation behavior in ternary La-Fe-Sb systems with binary Fe-Sb systems.
• Analysis of the impact of lanthanum addition on the nucleation of FeSb(2).

Main Results:

• Nucleation energy of La(0.5)Fe(4)Sb(12) strongly depends on the Fe/Sb ratio, increasing as it deviates from the 1:3 stoichiometric value.
• Lanthanum addition suppresses the nucleation of FeSb(2) in modulated reactants.
• The Fe/Sb composition range for ternary skutterudite nucleation is broadened by the presence of lanthanum.

Conclusions:

• The Fe/Sb ratio is a critical factor controlling the nucleation energy and formation of La(x)Fe(4)Sb(12) skutterudites.
• Lanthanum acts to inhibit the nucleation of binary FeSb(2), facilitating the formation of ternary compounds.
• These findings align with theoretical predictions and explain the nucleation of metastable phases from amorphous intermediates.