Effect of Chemical Bonding Characteristics on Ordering Structure in Li Spinel Oxides

Abstract

An ordered configuration between atoms is frequently observed in many alloys and complex ionic compounds, as the ordering structure is energetically more stable in terms of the lattice enthalpy. However, when the entropy effect becomes dominant with increasing temperature, the ordered configurational symmetry is subject to be thermally perturbed, resulting in a transition to a random distribution of atoms at elevated temperature. By comparing two Li(B ' B '')(2)O-4-type spinel oxides having an identical space group and analogous compositions, it can be elucidated that the locally distinct chemical bonding characteristics, which are substantially covalent versus highly ionic, make a significant contribution to the formation of ordering. More importantly, such ordering structure is considerably robust without perturbation even at very high temperature near the melting point. The findings in this work suggest that the locally different bonding nature is one of the critical structure-determining factors in complex oxides with multiple cations, emphasizing the significance of in-depth understanding of the correlation of electronic configurations with the overall crystalline structure.