Hole doping and structural transformation in CsTl1-xHgxCl3

Area of Science:

• Solid State Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Theoretical predictions suggested CsTlCl(3) and CsTlF(3) perovskites could become superconductors with hole doping.
• Pure CsTlCl(3) exists in tetragonal and cubic polymorphs, while CsTlF(3) is cubic.

Purpose of the Study:

• To investigate the potential for inducing superconductivity in CsTlCl(3) by substituting thallium (Tl) with mercury (Hg).
• To synthesize and characterize the series CsTl(1-x)HgxCl(3) to explore structural and electronic properties.

Main Methods:

• Synthesis of the solid solution series CsTl(1-x)HgxCl(3) for various Hg concentrations (x = 0.0 to 0.8).
• X-ray diffraction (XRD) for structural analysis and phase identification.
• X-ray absorption spectroscopy (XAS) to determine the valence states of Tl.
• Raman spectroscopy to analyze vibrational modes.
• First-principle calculations to assess electronic properties and stability.

Main Results:

• The crystal structure evolved from tetragonal to cubic with increasing Hg content.
• Solid solutions were not formed for all compositions (x = 0.4, 0.5).
• All synthesized CsTl(1-x)HgxCl(3) samples were found to be insulators, showing no signs of superconductivity.
• XAS confirmed a mixed-valence state of Tl(+) and Tl(3+) across the series.
• Raman spectroscopy revealed characteristic Tl-Cl-Tl and Tl-Cl-Hg vibrational modes.

Conclusions:

• Mercury is not an effective dopant for inducing superconductivity in the CsTlCl(3) system.
• The synthesized mercury-substituted perovskites are stable insulators in their ground state.
• Further research may be needed to explore alternative doping strategies or related materials for superconductivity.