Phase coexistence in CaCuxMn7-xO12CaCuxMn7-xO12 solid solutions

A phase diagram for CaCuxMn7-xO12CaCuxMn7-xO12 for x⩽0.7x⩽0.7 is presented. At room temperature CaCuxMn7-xO12CaCuxMn7-xO12 with x=0.10x=0.10 and 0.20 crystallizes in the trigonal space group R3¯ and shows the same charge ordering of Mn3+Mn3+ and Mn4+Mn4+ ions as has been found for undoped CaMn7O12CaMn7O12. The x=0.10x=0.10 and 0.20 compounds both show an apical-type Jahn–Teller distortion of the MnO6 octahedra around Mn3+Mn3+ ions. Both compounds undergo a structural phase transition to a high-temperature cubic structure (space group Im3¯) with coexistence of both phases between 375 and 415 K for x=0.10x=0.10 and between 10 and 380 K for x=0.20x=0.20. The domain sizes of the coexisting phases are at least 200 nm for both x=0.10x=0.10 and 0.20 compounds.

Schematic representation of the trigonal CaCuxMn7-xO12CaCuxMn7-xO12 unit cell shown in the rhombohedral setting of space group R3¯.Figure optionsDownload as PowerPoint slide