It has it all: Cu5Sb2SiO12 - seven crystallographic independent positions for Cu2+ in one compound
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Date
2017-02-01
Journal Title
Journal ISSN
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Publisher
Australian Institute of Physics
Abstract
Cu5Sb2SiO12 is the only copper – antimony silicate know so far. We were also able to grow single crystals of Cu5Sb2SiO12 using chemical transport reactions and to solve the crystal structure completely. The crystal structure of the compound is truly remarkable as it contains seven structurally independent Cu2+-positions, all of them showing different coordination spheres (typical distorted CuO6 octahedra, [2+2+2] coordination, 5-fold coordination and CuO8 with 4 medium and 4 long bonds [4+4]). This is a very unique and very promising situation, which could be used for partial oxidation and reduction of Cu analogous to Cu containing high temperature superconductors, as well as replacing Cu with other M2+ transition metals. An anti-ferromagnetic long range ordering of Cu2+ could be shown for Cu5Sb2SiO12 below 27 K. First NPD measurements without magnetic field at temperatures below the ordering temperature do not show any magnetic peaks, which should be observed for a long range antiferromagnetic ordering. Our own field-dependent measurements confirm the magnetic ordering, but the magnetic ordering is only clearly visible in susceptibility data with external fields of about 3 T and higher. Manganese and Cobalt doped versions of the copper-antimony silicate have been synthesised. Since there are seven crystallographic independent positions for Cu2+ with very different coordination spheres, there should be preferential sites for the Mn and Co to be incorporated into the structure. Lab X-ray and neutron powder diffraction data show that doping appears to work well up until Cu2Mn3Sb2SiO12. All materials have been synthesised at 900°C in air, a temperature where the stable ion should be Mn3+ rather than Mn2+, which can be seen in studies of the Cu5-xMnxSbO6 system. Mn doping leads to much stronger magnetic ordering in the compounds and the antiferromagnetic ordering could finally observed in neutron powder data.
Description
Keywords
Antimony compounds, Chalcogenides, Coherent scattering, Diffraction, Dimensionless numbers, Elements, Magnetism, Metals, Oxides, Oxygen compounds, Physical properties, Silicates, Silicon compounds, Transition element compounds
Citation
Olney, T., Wilson, D., Avdeev, M., & Söhnel, T. (2017). It has it all: Cu5Sb2SiO12 - seven crystallographic independent positions for Cu2+ in one compound. Paper presented to the 41st Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW, Australia, 31st January - 3rd February 2017, (pp. 33). Retrieved from: https://physics.org.au/wp-content/uploads/cmm/2017/Wagga_2017_Conference_Handbook.pdf