Ternary Zinc Antimonides Unlocked Using Hydride Synthesis

Area of Science:

• Solid-state chemistry and materials science.
• Exploration of ternary intermetallic compounds.

Background:

• Synthesis of novel materials is crucial for advancing various technological applications.
• Sodium zinc antimonides represent a class of compounds with potential applications in thermoelectric devices.

Purpose of the Study:

• To synthesize and characterize new ternary sodium zinc antimonides.
• To investigate the structural and physical properties of the newly discovered compounds.
• To evaluate the potential of using sodium hydride (NaH) as a reactive sodium source in solid-state synthesis.

Main Methods:

• Utilized sodium hydride (NaH) as a reactive sodium source for synthesis via ball-milling.
• Employed X-ray diffraction (XRD) for structural characterization, including single-crystal and in situ synchrotron powder XRD.
• Measured thermal conductivity, Seebeck coefficient, and electrical resistivity to assess thermoelectric properties.

Main Results:

• Successfully synthesized three new sodium zinc antimonides: Na$_{11}$Zn$_{2}$Sb$_{5}$, Na$_{4}$Zn$_{9}$Sb$_{9}$, and NaZn$_{3}$Sb$_{3}$.
• Na$_{11}$Zn$_{2}$Sb$_{5}$ crystallizes in the triclinic P1 space group featuring unusual 3-coordinated Zn atoms.
• Na$_{4}$Zn$_{9}$Sb$_{9}$ and NaZn$_{3}$Sb$_{3}$ crystallize in the monoclinic C2/m space group with complex framework structures built from distorted ZnSb$_{4}$ tetrahedra.
• Na$_{4}$Zn$_{9}$Sb$_{9}$ and NaZn$_{3}$Sb$_{3}$ exhibit low thermal conductivities (0.97-1.26 W·m$^{-1}$K$^{-1}$) and semimetallic electrical resistivities.
• These two compounds decompose into NaZnSb above ~800 K.

Conclusions:

• Sodium hydride (NaH) is an effective precursor for synthesizing complex sodium-containing intermetallic compounds, enabling better compositional control.
• The newly discovered Na-Zn-Sb compounds possess unique crystal structures and exhibit thermoelectric properties.
• The findings underscore the importance of selecting appropriate synthetic methods for discovering new materials in complex systems.