Phase coexistence in CaCuxMn7-O-x(12) solid solutions

摘要

A phase diagram for CaCuxMn7-xO12 for x <= 0.7 is presented. At room temperature CaCuxMn7-xO12 with x = 0.10 and 0.20 crystallizes in the trigonal space group R (3) over bar and shows the same charge ordering of Mn3+ and Mn4+ ions as has been found for undoped CaMn7O12. The x = 0.10 and 0.20 compounds both show an apical-type Jahn-Teller distortion of the MnO6 octahedra around Mn3+ ions. Both compounds undergo a structural phase transition to a high-temperature cubic structure (space group Im (3) over bar) with coexistence of both phases between 375 and 415 K for x = 0.10 and between 10 and 380 K for x = 0.20. The domain sizes of the coexisting phases are at least 200 nm for both x = 0.10 and 0.20 compounds. (c) 2006 Elsevier Inc. All rights reserved.