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Synthesis, Structure, and Properties of Sodium or Potassium-Doped Lanthanum Orthomanganites from NaCl or KCl Flux

Singh, Ram Niwas and Shivakumara, C and Vasanthacharya, NY and Subramanian, S and Hegde, MS and Rajagopal, H and Sequiera, A (1998) Synthesis, Structure, and Properties of Sodium or Potassium-Doped Lanthanum Orthomanganites from NaCl or KCl Flux. In: Journal of Solid State Chemistry, 137 (1). pp. 19-27.

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Abstract

Lanthanum and oxygen-deficient $La_{1-x-y}A_xMnO_{3-\delta}$(A=Na or K) ferromagnetic oxide phases have been synthesized from NaCl or KCl flux, starting from $La_2O_3$and $MnCO_3$ at 900°C. Composition of the final product could be varied by varying initial composition $La_yMnO_3(0.7<y<1)$. Final composition of these oxides was obtained from chemical analysis of elements present. As the lanthanum content increased, Na or K content decreased and the structure changed from rhombohedral to orthorhombic symmetry. $Mn^{4+}$ concentration was 27% in the sodium doped manganite, $La_{0.82}Na_{0.13}MnO_{2.93}$ with Curie temperature 325 K, and $Mn^{4+}$ was 25% in the potassium doped $La_{0.82}K_{0.08}MnO_{2.89}$ with $T_c$ of 310 K. Structure of these two phases have been refined from neutron diffraction studies. Stoichiometric $La_{1-x}A_xMnO_3$(A=Na or K) have been obtained for the initial composition $La_yMnO_3(y=0.85)$. Orthorhombic phases obtained were found to be Mn-deficient $La_{1-x}Na_xMn_{1-x}Mn_{1-y}O_3$ $(x {\simeq}0.02;y{\simeq}0.05)$, which were ferromagnetic insulators, even though total $Mn^{4+}$contents were as high as 29%.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 27 Feb 2007
Last Modified: 19 Sep 2010 04:32
URI: http://eprints.iisc.ernet.in/id/eprint/8832

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