The Effects of Ca and Mn Excess Co-Doping in CMR Manganites Solid Solution Structures

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A comprehensive study of CMR manganite related phases, particularly those that develop under the effects of Ca and Mn-excess co-doping is undertaken. The relationships between phase composition, processing and observed crystalline structure are investigated for co-precipitated powders of composition La1-xCaxMn1+zO3+δ, thermally treated at 800 and 1000 °C in air for Ca contents of x=0.10 and x=0.15 and Mn content from z=0 up to z=0.88. A relevant structural transition from orthorhombic to rhombohedric symmetry is observed as a function of Mn excess near 25% A site vacancies. This solid solution is in equilibrium with the conjugated phases, either LaMn7O12 at 800°C, or Mn3O4 at 1000°C, respectively. Results suggest that at the polymorphic phase transition the solid solution is stable enough to slow down Mn diffusion into the perovskite cell. Ca-doping introduces stability in the perovskite structure and broadens the domain for phase formation reaction. The solid solution limit of the Ca-manganite solid solution is set above 50% Mn excess.

Info:

Periodical:

Materials Science Forum (Volumes 514-516)

Edited by:

Paula Maria Vilarinho

Pages:

294-298

DOI:

10.4028/www.scientific.net/MSF.514-516.294

Citation:

F. Figueiras et al., "The Effects of Ca and Mn Excess Co-Doping in CMR Manganites Solid Solution Structures", Materials Science Forum, Vols. 514-516, pp. 294-298, 2006

Online since:

May 2006

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$35.00

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