Phase formation mechanism and kinetics in solid-state synthesis of undoped and calcium-doped lanthanum manganite

Journal Article · Thu Mar 05 04:00:00 EST 2009 · Materials Research Bulletin

OSTI ID:21199709

Jiayun, Zhang; Baijun, Yan; Jianhua, Liu ^[1]

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1. Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

LaMnO{sub 3+{delta}} and La{sub 0.7}Ca{sub 0.3}MnO{sub 3} were synthesized from La{sub 2}O{sub 3}(La(OH){sub 3}), CaCO{sub 3} and MnO{sub 2} powder mixture with solid-state reaction technique. X-ray diffraction and thermal analysis were employed in the present study on the process of synthesizing of the two compound powders. The kinetic study on solid-state reaction between La{sub 2}O{sub 3} and MnO{sub 2} in the powder mixture was isothermally carried out for LaMnO{sub 3+{delta}} formation. The result showed that the reaction process was controlled by three-dimensional solid-ionic diffusion. Both Jander and Ginstling-Brounstein model can be used to describe the reaction kinetics satisfactorily. The relevant apparent activation energy values obtained were as great as 205 {+-} 11 and 189 {+-} 8 kJ/mol. The reaction process of La{sub 0.7}Ca{sub 0.3}MnO{sub 3} preparation from La{sub 2}O{sub 3}, SrCO{sub 3} and MnO{sub 2} powder mixture was also studied using X-ray diffraction and thermal analysis. The result indicated that the following steps composed the overall reaction: the decomposition of the reactant; the formation of La{sub 1-x}Ca{sub x}MnO{sub 3+{delta}}; La{sub 2}O{sub 3} and Mn{sub 3}O{sub 4} reacted with La{sub 1-x}Ca{sub x}MnO{sub 3} to form final La{sub 0.7}Ca{sub 0.3}MnO{sub 3} phase. The latest step was the most time-consuming one among others in the overall reaction.

• OSTI ID: 21199709
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 3 Vol. 44; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
CALCIUM
CALCIUM CARBONATES
CERAMICS
DECOMPOSITION
DIFFUSION
DOPED MATERIALS
LANTHANUM HYDROXIDES
LANTHANUM OXIDES
MANGANESE OXIDES
REACTION KINETICS
STRONTIUM CARBONATES
SYNTHESIS
THERMAL GRAVIMETRIC ANALYSIS
X-RAY DIFFRACTION