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Th 7 Fe 3 ‐Type Related Structures in Pd(Pt)‐Cu‐B Systems: Pd 6 CuB 3 —A New Structure Type for Borides
Author(s) -
Salamakha Leonid P.,
Sologub Oksana,
Stöger Berthold,
Rogl Peter F.,
Waas Monika,
Michor Herwig,
Bauer Ernst
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201602767
Subject(s) - crystallography , octahedron , crystal structure , type (biology) , metal , materials science , transition metal , chemistry , metallurgy , geology , paleontology , biochemistry , catalysis
A new member of the series of Th 7 Fe 3 ‐type derivative structures, h ‐(Pd 0.86 Cu 0.14 ) 7 B 3 (≡Pd 6.02 Cu 0.98 B 3 , unique structure type Pd 6 CuB 3 , space group P 6 3 cm , a =12.9426(9) Å, c =4.8697(4) Å, single‐crystal X‐ray diffraction (XRD) data) was obtained from as cast alloys and alloys annealed at 600–650 °C. Further substitution of Cu by Pd led to formation of a Mn 7 C 3 ‐type structure, o ‐(Pd 0.93 Cu 0.07 ) 7 B 3 (≡Pd 6.51 Cu 0.49 B 3 , space group Pnma , a =4.8971(2) Å, b =7.5353(3) Å, c =12.9743(6) Å, single‐crystal XRD). Isotypic LT h ‐(Pt 0.70 Cu 0.30 ) 7 B 3 (≡Pt 4.90 Cu 2.10 B 3 ) was observed in the Pt‐Cu‐B system as a low‐temperature (LT) phase (T≤600 °C) (powder XRD), whereas the Th 7 Fe 3 ‐type (high‐temperature (HT) h ‐(Pt 0.73 Cu 0.27 ) 7 B 3 ≡Pt 5.11 Cu 1.89 B 3 , space group P 6 3 mc , a =7.4671(1) Å, c =4.9039(1) Å, powder XRD) proved to be stable at high temperature. The three structures are built of columns of face connected metal octahedra and columns of metal tetrahedra alternatingly fused by common faces and vertices. Boron atoms are found in trigonal prisms formed by metal atoms. The volumes of the three new Th 7 Fe 3 ‐type derivative borides relate as 1:2:3. Superconductivity was discovered for Pt 4.9 Cu 2.1 B 3 (Pd 6 CuB 3 ‐type) and Pt 5.1 Cu 1.9 B 3 (Th 7 Fe 3 ‐type) below 0.67 and 0.66 K, respectively. Despite the close value of the transition temperature the values of the upper critical field at 0 K differ as 0.37 T and 0.27 T for the two compounds.