Th₇ Fe₃ -Type Related Structures in Pd(Pt)-Cu-B Systems: Pd₆ CuB₃ -A New Structure Type for Borides

Area of Science:

• Materials Science
• Solid State Chemistry
• Condensed Matter Physics

Background:

• Exploration of ternary borides with transition metals is crucial for discovering new materials with unique structural and electronic properties.
• The Th₇Fe₃ structure type serves as a foundational model for a series of related derivative structures in intermetallic compounds.

Purpose of the Study:

• To synthesize and characterize new ternary boride phases in the Pd-Cu-B and Pt-Cu-B systems.
• To investigate the structural relationships and crystallographic properties of these newly discovered borides.
• To explore the superconducting properties of the synthesized platinum-copper-boron compounds.

Main Methods:

• Synthesis of alloys through casting and annealing processes.
• Single-crystal and powder X-ray diffraction (XRD) for structural determination.
• Measurement of superconducting transition temperatures and upper critical fields.

Main Results:

• Discovery of a new Th₇Fe₃-type derivative structure, h-(Pd_0.86Cu_0.14)₇B₃ (Pd₆CuB₃-type), and a Mn₇C₃-type structure, o-(Pd_0.93Cu_0.07)₇B₃.
• Identification of low-temperature (LT) and high-temperature (HT) isotypic phases in the Pt-Cu-B system: LT h-(Pt_0.70Cu_0.30)₇B₃ and HT h-(Pt_0.73Cu_0.27)₇B₃.
• Superconductivity observed in Pt_4.9Cu_2.1B₃ and Pt_5.1Cu_1.9B₃ below 0.67 K and 0.66 K, respectively, with differing upper critical fields.

Conclusions:

• The study successfully synthesized and structurally characterized novel ternary borides, expanding the known Th₇Fe₃-type derivative structures.
• The structural complexity and phase relationships in these metal-rich borides were elucidated.
• The discovery of superconductivity in Pt-Cu-B compounds highlights their potential for low-temperature electronic applications.