Structural investigation of the disordered Cu_3-xSbO_5.5+y ternary oxide

Full text: Many different electrolytes with perovskite and fluorite-type structures have been extensively explored and characterised. Minimal focus has been given to potential Bixbyite-type electrolytes. A ternary copper antimony oxide previously referred to as Cu₉Sb₄O₁₉ with an unresolved crystal structure looked like a promising candidate to study. This was synthesised using classic solid state techniques under high temperature and oxygen pressure. Refinement of lab X-ray diffraction data strongly indicated that this material was isostructural with Cu₃TeO₆ with a curiously large degree of oxygen vacancies. Refinement of neutron diffraction patterns revealed the system was much more complicated than first anticipated, confirming the under occupancy of oxygen and revealing the mixed occupation of Cu²⁺/Sb⁵⁺ sites in the cationic sub-lattice. The final composition can be refined to Cu_3−xSbO_5.5+3x/2 X-ray absorption experiments confirmed the local coordination significantly differs from Cu₃TeO₆ complimenting the diffraction data. This is an interesting material in a good position for many potential applications like; oxygen membranes, sensors or as a cathode/electrolyte material warranting further investigation. (author)