Rapid Synthesis of Ferromagnetic $La_{1-x}Na_xMnO_3$ $(0.00\leq x\leq 0.25)$ by the Solution Combustion Method

Shivakumara, Chikkadasappa and Bellakki, Manjunath B and Prakash, Annigere S (2007) Rapid Synthesis of Ferromagnetic $La_{1-x}Na_xMnO_3$ $(0.00\leq x\leq 0.25)$ by the Solution Combustion Method. In: Journal of the American Ceramic Society, 90 (12). pp. 3852-3858.

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Abstract

Rapid synthesis of sodium-substituted lanthanum manganite phases is reported by the solution combustion method using oxalyl dihydrazide (ODH), as fuel. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800°C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder X-ray diffraction data. Parent $LaMnO_3$ compound crystallizes in the orthorhombic structure (space group Pbnm No. 62). Sodium-substituted compounds crystallize with rhombohedral symmetry (space group R-3c, No.167). On increasing the sodium content, unit cell volume decreases and Mn–O–Mn bond angle increases. The fourier transform infrared spectrum shows two absorption bands around 600 and $400 cm^{−1}$ for the compositions x=0.0, 0.05, and 0.10. $Mn^{3+}/Mn^{4+}$ ratio was determined by iodometric titration. Electrical resistivity measurements reveal a composition-controlled metal to insulator transition $(T_{M-I})$, the maximum $T_{M-I}$ was observed for the composition $La_{0.85}Na_{0.15}MnO_3$ at 285 K. Increase in magnetic moment is observed with increase in crystallite size. Room temperature vibrating sample magnetometer data indicate that for the composition up to x=0.10, the compounds are paramagnetic whereas composition with x=0.15, 0.20, and 0.25 show magnetic moments 34, 39, and 33 emu/g, respectively.

Item Type: Journal Article Copyright of this article belongs to Blackwell Synergy. Division of Chemical Sciences > Solid State & Structural Chemistry Unit 06 Jun 2008 27 Aug 2008 13:26 http://eprints.iisc.ernet.in/id/eprint/14218