Thermodynamics of copper‐manganese and copper‐iron spinel solid solutions

Abstract

High-temperature oxide melt solution calorimetry has been performed to investigate the energetics of spinel solid solutions in the Mn 3 O 4 -CuMn 2 O 4 and Fe 3 O 4 -CuFe 2 O 4 systems. The spinel solid solutions were synthesized by a ceramic route and calcined at appropriate temperatures to obtain single phase samples. The drop solution enthalpies of the solid solutions in the Mn 3 O 4 -CuMn 2 O 4 system are the same within experimental error as the enthalpies of drop solution of mechanical mixtures of the end-members, indicating a zero heat of mixing, i.e., ideal mixing in terms of enthalpy. In Fe 3 O 4 -CuFe 2 O 4 , the drop solution enthalpy of the solid solutions shows a positive deviation from those of the mechanical mixture of the end-members, suggesting negative mixing enthalpy. The formation enthalpies of the spinel solid solutions from their constituent oxides plus oxygen and from the elements were also determined.

Thermodynamic and Structural Properties of CuCrO2 and CuCr2O4: Experimental Investigation and Phase Equilibria Modeling of the Cu–Cr–O System

“…This also suggests that the cationic distribution is not affected by the composition. This is notably different from the Cu–Fe–O system, for which we have shown previously that the lattice constants of the spinel phase Cu x Fe 3– x O 4 depend on the composition, , which is a strong indicator of a nonstoichiometry of the phase.…”

“…This also suggests that the cationic distribution is not affected by the composition. This is notably different from the Cu−Fe−O system, for which we have shown previously that the lattice constants of the spinel phase Cu x Fe 3−x O 4 depend on the composition, 84,85 which is a strong indicator of a nonstoichiometry of the phase. HT-XRD and Rietveld analysis coupled with TGA−DTA in air in the 50−1100 °C temperature range allow us to confirm the existence of the mixed phases described by the literature in this system.…”

Experimental and Thermodynamic Study on the Interaction of Copper Oxygen Carriers and Oxide Compounds Commonly Present in Ashes

“…Spinel metal oxides such as CuFe 2 O 4 have a high catalytic performance during combustion, and they can also be used as oxygen carriers. , It is known that CuFe 2 O 4 can form over CuO and Fe 2 O 3 above 900 °C. To form Fe-included CuO- and Cu 2 O-based solid solutions, higher temperatures are needed. , …”

“…When Al 2 O 3 and Fe 2 O 3 were used as oxide compounds, a strong interaction was observed for both the experiment and TEC. Some of the formed compounds could be considered as oxygen carriers, so these oxide compounds would not cause any serious problem. , However, the loss of CuO/Cu 2 O would result in a loss of CLOU properties which can severely decrease the fuel conversion efficiency.…”

Insights on the Stability and Cationic Nonstoichiometry of CuFeO2 Delafossite

“…A large amount of research effort during the last decade has focused on the cuprospinel phase Cu z Fe 3– z O 4 , a well-known inverse spinel structure with cubic (space group Fd 3̅ m ) or tetragonal (space group I 4 1 / amd ) symmetry depending on the temperature and consisting of a solid solution between copper ferrite ( z = 1, i.e., CuFe 2 O 4 ) and magnetite ( z = 0, i.e., Fe 3 O 4 ). Fe-based spinels have been widely described in the literature because of their magnetic, electrical, and optical properties, with applications in catalysis − and battery electrodes , among others. − …”