Syntheses and properties of a family of new compounds RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} (RE=La, Pr, Nd, Sm–Ho) with an ordered pyrochlore structure

• Published in: Journal of solid state chemistry Vol. 217
• Main Authors: Li, Kuo, Hu, Yufei, Wang, Yingxia, Kamiyama, Takashi, Wang, Bingwu, Li, Zhaofei, Lin, Jianhua
• Format: Journal Article
• Language: English
• Published: United States 15.09.2014
• Subjects: ANTIMONY IONS; CARBON 17; CATIONS; COBALT IONS; DISTRIBUTION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INTERACTIONS; LANTHANUM IONS; MAGNETIC SUSCEPTIBILITY; NEUTRON DIFFRACTION; PYROCHLORE; RARE EARTHS; RHENIUM IONS; SPACE GROUPS; SPECTROSCOPY; SPIN; SYNTHESIS; TRANSITION ELEMENTS; TRIGONAL LATTICES; X-RAY DIFFRACTION; ZINC IONS
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/J.JSSC.2014.05.003

Isostructural compounds RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} (RE=La, Pr, Nd, Sm–Ho) with an ordered pyrochlore structure were synthesized. The structure of La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} was solved ab initio based on powder XRD data, and refined by combining with high resolution neutron diffraction data. La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} crystallizes in the space group R-3m with the unit cell parameters a=7.52954(2) Å and c=17.59983(6) Å. The structures of other members in this family are confirmed by Rietveld refinement using powder X-ray diffraction data. The cations (RE, Sb and Co) in RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} are orderly distributed, presenting as [RE{sub 3}Co][Sb{sub 3}Co]O{sub 14} formula, and giving rise to two distinctive Kagome lattices constructed by RE{sup 3+} and Sb{sup 5+}, respectively. Co{sup 2+} occupies 8-coordinated and 6-coordinated environments, showing low spin (S=1/2) and high spin (S=3/2) states respectively. The magnetic susceptibility and UV–visual spectroscopy supports the magnetic observation. TDDFT calculation was performed to interpret the electronic states. The compounds [RE{sub 3}Co][Sb{sub 3}Co]O{sub 14} provide a profound example in which the ideal 2D Kagome lattice is derived from the 3D pyrochlore-type structure by an ordered distribution of the metal cations. - Graphical abstract: La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} crystallizes in a pyrochlore related structure with an ordered distribution of cations, giving rise to two sets of ideal 2D Kagome lattices formed by La{sup 3+} or Sb{sup 5+} respectively. This rhombohedral pyrochlore is a tolerant structure for stable compounds composed by many light rare-earth and d-transition elements. Substituting Zn{sup 2+} or Mg{sup 2+} for Co{sup 2+} will provide a series of compounds useful for studying magnetic interactions in the rare-earth Kagome lattices. - Highlights: • Pyrochlore-type La{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} shows an ordered distribution of cations in its structure. • It presents two sets of ideal 2D Kagome lattices formed by La{sup 3+} or Sb{sup 5+}, respectively. • A family of isostructural compounds RE{sub 3}Sb{sub 3}Co{sub 2}O{sub 14} (RE=Pr, Nd, Sm–Ho) were realized. • Co{sup 2+} presents two spin states with S=1/2, 3/2 due to two coordinated environments.