Phase Equilibria in the System CuMnO

Abstract

A T‐x‐section of the phase diagram is proposed for the system CuMnO in air between 750 and 1,400°C. From X‐ray and chemical analyses on quenched samples and from high‐temperature X‐ray diffraction studies the occurrence of the following phases is deduced: a cubic phase α‐Mn2O3, a phase CuxMn3−xO4+γ (0 ⩽ x < 0.2 and 0 < γ < 0.02) with a tetragonally deformed spinel structure, a cubic spinel phase CuxMn3−xO4+γ (0 ⩽ x ⩽ 1.03 and −0.08 < γ < 0.02), a crednerite‐like phase CuyMn1−yO (0.50 < y < 0.53) with monoclinic structure, a delafossite‐like phase CuyMn1−yO (0.54 < y < 0.60) with hexagonal structure, a liquid phase, the phase Cu2O and the phase CuO. CuMn2O4 was found to be cubic or tetragonal at room temperature, depending on the temperature of quenching. The po2‐x‐section of the system CuMnO at 1,000°C, as determined by SCHMAHL and MÜLLER (1964), was confirmed and could be farther extended to lower oxygen pressures. The valencies of the cations, especially of those in the spinel structure, are discussed.

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

“…It was demonstrated that CuMnO 2 is unstable at 1150°C. This is quite consistent with previous results [8,18]. In situ high-temperature XRD measurements show that CuMnO 2 at high temperatures has rhombohedral structure, not monoclinic, contrary to earlier literature.…”

“…Driessens and Rieck [18] investigated the interaction of copper and manganese oxides in air between 750 and 1400°C and reported Cu 1?x Mn 1-x O 2 to be a credneritelike phase with monoclinic structure (0 \ x \ 0.06) and a delafossite-like phase with hexagonal structure (0.08 \ x \ 0.12). At 1060 ± 10°C, the delafossite structure was reported to decompose.…”

Formation of Copper–Manganese Oxides from CuxMn1−x(HCOO)2·2H2O Mixed Crystals

“…4e). The other formate samples could form Cu V Mn \V O (where x(1) homogeneous spinel phases under harder conditions (heating to temperature above 900-1000°C, then cooling at 700-800°C, and quenching in water), according to the scheme given in (14,19).…”

Preparation and physical properties of the solid solutions Cu1+xMn1−xO2 ()

“…They reported that the phases formed from various mixtures of CuO Schmall and Mu¨ller mentioned the compound Cu 1+x Mn 1ÀxÀd O 2+d (x ¼ 0:06 and d ¼ 0:048) [11]. Driessens and Rieck have extended the temperature range investigating the interaction of CuO and MnO oxides in air between 750 and 1400 1C [12]. In addition to the phases cited above the authors reported on a solid solution Cu 1+x Mn 1Àx O 2 having a crednerite structure for 0pxp0:06 and a delafossite structure for 0:08pxp0:12.…”