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Studies on surface composition and chemical states of calcium manganites

Kumar, Sanjiv and Raju, VS and Bera, Santanu and Vijaynandhini, K and Kutty, TRN (2005) Studies on surface composition and chemical states of calcium manganites. In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 237 (3-4). pp. 623-630.

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Abstract

This paper describes investigations on atomic composition and chemical states of sintered calcium manganites discs in surface and near surface regions. The atomic composition was determined by 3.05 MeV O-16(alpha,alpha)O-16 resonance elastic scattering while the chemical states by,X-ray photoelectron spectroscopy (XPS). The specimens examined included undoped and donor (Y3+, Bi3+) doped CaMnO3, and Ca-excess and Mn-excess manganites namely Ca2MnO4 and CaMn2O4 respectively. Calcium manganite powder used in the preparation of discs was synthesized by a wet chemical method. X-ray diffraction (XRD) results indicated that all the discs are monophasic except CaMn2O4, which contained similar to 98% requisite manganite. The atomic compositions of undoped specimens areclose to the stoichiometric value while Y3+ and Bi3+ doped specimens are deficient in Mn and O respectively. The O deficiency may be responsible for comparatively higher electrical conductivity of Bi3+ doped specimen. Some of the specimens were also examined subsequent to their annealing in low P-O2 atmosphere. This treatment produced significant compositional and structural modifications in the near surface regions. Mn(2p) electrons have identical binding energies in the sintered discs; therefore the valence states of Mn could not be discerned. However lesser binding energies of these electrons inannealed CaMnO3 indicated the existence of Mn(II)/Mn(III) in thespecimen.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Elsevier.
Keywords: Calcium manganite;Backscattering spectrometry;X-ray photoelectron spectroscopy;Composition;Reduction
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Date Deposited: 06 Oct 2005
Last Modified: 19 Sep 2010 04:20
URI: http://eprints.iisc.ernet.in/id/eprint/3789

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