Structural investigation of oxygen-deficient perovskite CaMnO2.75

Thermoelectric properties of CaMnO3 films obtained by soft chemistry synthesis

“…The nonstoichiometry of the films is accumulated at the surface of the crystallized films in every layer. The presence of a brownmillerite-type CaMnO 2.75 phase 4 detected by GIRXD (Fig. 3) could be the origin of the resistivity and Seebeck value reduction.…”

“…2 Perovskite-type manganates are well known for their high magnetoresistance which can be explained by the double-exchange model. Calcium manganate, CaMnO 3 , is an antiferromagnetic insulator that was intensively studied in recent years in terms of colossal magnetoresistance (CMR), 3,4 thermoelectricity, [5][6][7][8] and its suitability as oxygen sensor. 9 The CMR effect of perovskite manganates results from charge and/or orbital ordering and the competition between different magnetic interactions.…”

Nonstoichiometry and reductive decomposition of CaMnO

“…The structure of CaMnO 2.5 is built from corner shared MnO 5 -square pyramids. Rietveld refinement of time-of-flight neutron diffraction data show that the structure of the intermediate compound CaMnO 2.75 consists of 50% octahedra and 50% square pyramids [3]. This interpretation is supported also by high-resolution electron microscopy that shows that both CaMnO 2.75 and CaMnO 2.8 contain corner-linked MO 6 -octahedra and MO 5 -square pyramids [4][5][6].…”

“…The stoichiometric compound CaMnO 3 is orthorhombic at room temperature and takes a perovskiterelated structure based on corner-shared MnO 6 -octahedra [2]. Structures with low symmetry and long-range ordered arrangements of the oxygen-vacancies can be produced under reducing conditions, e.g., CaMnO 2.5 [2], CaMnO 2.75 [3] and CaMnO 2.8 [4]. The structure of CaMnO 2.5 is built from corner shared MnO 5 -square pyramids.…”

Room temperature large positive and negative magnetocapacitance in CaMn0.95Fe0.05O3−δ

“…Parent composition (x¼0.0) and Fe doped composition (x¼0.05) show some extra peaks (indicated by n , for x¼0.05 less extra peaks) which are originated due to the presence of oxygen non-stoichiometry in lattice. We have found the oxygen content was greater than 2.8 in x¼0.0 composition after comparing with the XRD pattern of CaMnO 3À δ (0.0rδr0.2) [12]. CaMnO 3À δ and LaMnO 3À δ compounds are known to show the presence of mixed valences Mn 3 þ /Mn 4þ when prepared in open air at high Contents lists available at ScienceDirect…”