Cation Valencies and Distribution in the Spinels NiMn2O4 and MzNiMn2−zO4 (M = Li, Cu) Studied by XPS

Abstract

Photoelectron spectroscopic investigations (XPS) of the spinels NiMn2O4 and MzNiMn2−zO4 (M = Li, Cu) in comparison with Mn2TiO4, ZnMn2O4, and MgNiMnO4, containing Mn in only one oxidation state, show that in the former compounds MnII, MnIII, and MnIV are present. By a fitting process yielding the amounts of the Mn ions in the different oxidation states it is possible to determine the cation distribution of NiMn2O4 which is characterized by a high inversion parameter and a considerable degree of disproportionation. Cation valencies and their distribution in the substituted spinels are discussed. An increasing concentration of MnIV with higher values of z is reflected in the spectra by shift of the Mn p signals and by changes in their shape.

Study of the preparation conditions for NiMn2O4 grown from hydroxide precursors

“…Thus the increase of the oxygen B values with increasing firing temperature may be due to an increase in the proportion of the B sites occupied by Mn 3+ ions. This is in accordance with reports of the cation distribution, 33,34 rameter with temperature. 11,28 Also, any loss of nickel from NiMn 2 O 4 (for example, by the segregation of NiO) will act to increase the amount of the B sites occupied by Mn 3+ .…”

Thermodynamic assessment of the Mn–Ni–O system

“…Some authors conclude a total inverse structure (n = 1) [28,29], while others find a partial inverse structure [30,31]. Boucher [32] found a temperature dependence of n, ranging from n = 0.74 to n = 0.93 [33 -36] found large amount of Mn +4 in this structure.…”

Microwave-assisted optimization of the manganese redox states for enhanced capacity and capacity retention of LiAlxMn2−xO4 (x = 0 and 0.3) spinel materials

“…XPS is a well-known surface-sensitive technique for the quantication of cations in oxide materials including spinels. [31][32][33][34][35][36][37][38][39] From the Mn 2p 3/2 spectra of the spinel materials (Fig. 5) ).…”