Structural studies of technetium-zirconium alloys by X-ray diffraction, high-resolution electron microscopy, and...

Area of Science:

• Materials Science
• Solid State Physics
• Computational Materials Science

Background:

• Understanding binary alloy phase diagrams is crucial for materials development.
• Technetium-Zirconium (Tc-Zr) alloys are of interest for their unique structural properties.

Purpose of the Study:

• To investigate the structural properties and phase behavior of Tc-Zr binary alloys.
• To elucidate the bonding characteristics and stability of Tc-Zr phases using computational methods.

Main Methods:

• Combined experimental techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM).
• Computational approaches utilizing Rietveld analysis and density functional theory (DFT) calculations.

Main Results:

• Tc(6)Zr crystallizes in a cubic alpha-Mn-type structure with variable stoichiometry (Tc(6.25-x)Zr).
• Tc(2)Zr exhibits a hexagonal MgZn(2)-type structure.
• Lattice parameter of Tc(6)Zr increases linearly with Zr content, attributed to Zr substitution for Tc.
• DFT calculations reveal dominant Tc 4d orbital contributions near the Fermi level and identify strong d-d sigma bonds in Tc(2)Zr.

Conclusions:

• The variable stoichiometry of the Tc(6)Zr phase necessitates its inclusion in the Tc-Zr phase diagram.
• The structural stability of Tc-Zr alloys is influenced by strong d-d bonding, particularly in Tc(2)Zr.