Synthesis and structural characterization of CuAl2O4 spinel with an unusual cation distribution

  • Yajie Liu
  • Shaojun Qing
  • Xiaoning Hou
  • Gang Feng
  • Rongbin Zhang
  • Xiang Wang
  • Shanmin Wang
  • Zhixian Gao
  • Hongwei Xiang
Keywords: Spinel; Crystal structure; Nuclear magnetic resonance; Extended X-ray absorption fine structure


A CuAl2O4 spinel with unusual cation distribution has been synthesized for the first time by the solid phase reaction of copper hydroxide and pseudo-boehmite with both stoichiometric (Cu/Al = 1/2) and non-stoichiometric (Cu/Al = 1/3) ratios. Instead of characterizing one cation for the determination of cations distribution as generally performed in previous literatures, both cations in the synthesized spinel have been characterized with 27Al NMR for Al ions and EXAFS for Cu ions, respectively. The characterization data reveal that nearly all Al3+ ions are octahedrally coordinated while most Cu2+ occupy the tetrahedral sites, giving a (Cu0.8)[Cu0.2Al2]O4 spinel which has been supported by the Rietveld refinement. The unusual cation distribution, which has been rarely reported before, presents abnormal site occupancies in Cu-Al spinel oxide. Hence, the findings of this work may invoke further explorations on other spinel oxides for targeting novel distinctive properties and applications.