Abstract

A new double perovskite Ca2FeMnO6 with a layered arrangement of Mn4+ and the unusually high-valence Fe4+ was obtained by oxidizing the precursor brownmillerite Ca2FeMnO5 with ozone at 200 °C. This low-temperature topotactic reaction kept the layered cation arrangement of the brownmillerite but oxidized Mn3+ to Mn4+ and Fe3+ to Fe4+. The crystal structure with a P21/c space group was revealed by detailed structure analysis with neutron powder diffraction data, and the layered arrangement of the cations was confirmed in an STEM-EELS elemental mapping image. The fully oxidized chemical composition was also confirmed by thermogravimetric analysis. Even with the two-dimensional layered arrangement, the instability of the unusually high-valence Fe4+ in Ca2FeMnO6, like that of the Fe4+ in the perovskites CaFeO3 and CaCu3Fe4O12 with three-dimensional arrangements of Fe4+, was relieved by charge disproportionation (2Fe4+ → Fe3+ + Fe5+) at a low temperature.

This content is only available as a PDF.
This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://dbpia.nl.go.kr/pages/standard-publication-reuse-rights)
You do not currently have access to this article.