The effects of Ca and Mn excess co-doping in CMR manganites solid solution structures
authors Figueiras, F; Vieira, JM; Guzik, ME; Legendziewicz, J; Tavares, PB; Amaral, VS
editors Vilarinho, PM
nationality International
journal ADVANCED MATERIALS FORUM III, PTS 1 AND 2
author keywords manganites; solid solution; vacancies; crystalline structures
keywords NONSTOICHIOMETRY; LA; ND
abstract 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+delta, thermally treated at 800 and 1000 degrees 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 degrees C, or Mn3O4 at 1000 degrees 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.
publisher TRANS TECH PUBLICATIONS LTD
issn 0255-5476
year published 2006
volume 514-516
beginning page 294
ending page 298
web of science category Materials Science, Multidisciplinary
subject category Materials Science
unique article identifier WOS:000238056400061

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