In situ high-temperature X-ray and neutron diffraction of Cu–Mn oxide phases

Abstract

Copper-manganese oxides were analyzed by in situ high-temperature powder neutron and X-ray diffraction to investigate their crystal structure. Cu-Mn spinel was found to form a continuous solid solution with cubic symmetry between Mn 3 O 4 and Cu 2 MnO 4 . A high-temperature phase with approximate composition Cu 5 Mn 4 O 9 was shown to have hexagonal symmetry. The cation distribution and lattice parameters of Cu-Mn spinel were resolved through Rietveld refinement of in situ neutron diffraction data. The results demonstrated that the Cu ion has a lower octahedral site preference than manganese ions, and quenching is not a reliable method to determine the equilibrium structure in the system.

Oxygen storage capacity and thermal stability of the CuMnO2–CeO2 composite system

“…22 However, it has been reported that Cu 1+x Mn 1Àx O 2 (0.08 < x < 0.12) at high temperature can exhibit a delafossite-like phase with a hexagonal structure because the thermal expansion of the structure would result in a larger lattice distortion than that from the Jahn-Teller effect. 23,24 It is well known that multiple valences of Mn cations can coexist in many Mn-containing compounds, which could be benecial to the oxygen-storage properties. [25][26][27] The valence of Mn in CuMnO 2 has been demonstrated to be +3, however the existence of Mn 4+ in the nonstoichiometric Cu 1+x Mn 1Àx O 2 oxides is also detected by XPS because the excess Cu atoms would occupy the octahedral site with Cu 2+ while the electrical neutrality principle would result in the formation of mixed Mn 3+ /Mn 4+ .…”

Catalytic combustion of SOFC stack flue gas over CuO and Mn2O3 supported by La0.8Sr0.2Mn0.67Cu0.33O3 perovskite

“…The XRD patterns of fresh, 650, and 800°C‐exposed CuMnLa/Alumina are shown in Figure . When CuMnLa/Alumina was exposed to 650°C of SOFC stack flue gas for 24 h, CuO peaks disappeared and CuMn 2 O 4 spinel peaks appeared . Therefore, the deactivation at 650°C in Figure appears to be attributed to the phase transition of amorphous Cu‐Mn to the spinel structure .…”

EPR Study of Dealuminated HY Zeolite and Silica Containing Cu-Mn-Zn Spinels: The Effect of Support

“…The cations are distributed among two sublattices, one formed by the four-oxygen-coordinated tetrahedral A sites, and the other by the six-oxygen-coordinated octahedral B sites. It has been shown [1][2][3][4] or Mn 3+ cations become elongated as a result of the Jahn-Teller effect.…”