Ternary Chalcogenides BaMTe₂ (M = Cu, Ag): Syntheses, Modulated Crystal Structures, Optical Properties, and...

Area of Science:

• Solid-state chemistry and crystallography
• Materials science and condensed matter physics

Background:

• Barium telluride compounds are of interest for their diverse structural and electronic properties.
• Understanding the crystal structure and electronic behavior of novel tellurides is crucial for materials development.

Purpose of the Study:

• To synthesize and characterize new barium-copper-telluride (BaCuTe2) and barium-silver-telluride (BaAgTe2) compounds.
• To determine the crystal structures and investigate the physical properties of these novel materials.

Main Methods:

• Solid-state synthesis at high temperatures (1173 K).
• Single-crystal X-ray diffraction for crystal structure determination.
• Raman and UV-vis-NIR spectroscopy for vibrational and electronic properties.
• Density Functional Theory (DFT) calculations for electronic structure analysis.

Main Results:

• Black crystals of BaCu0.43(3)Te2 and BaAg0.77(1)Te2 were successfully synthesized.
• Both compounds exhibit modulated crystal structures, with BaCu0.43(3)Te2 in a monoclinic superspace group and BaAg0.77(1)Te2 in an orthorhombic superspace group.
• Spectroscopic studies revealed Ag-Te and Ba-Te vibrations, and a direct band gap of 1.0(2) eV for BaAg0.8Te2, confirming its semiconducting nature.
• DFT calculations indicated a pseudo bandgap with low density of states at the Fermi level.

Conclusions:

• The synthesis and structural elucidation of BaCuTe2 and BaAgTe2 provide new insights into barium-telluride systems.
• The observed modulated structures and semiconducting behavior highlight the potential of these materials for further research and applications.