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34 results on '"Kharlamova, M. V."'

33. Phase transition in nanostructured LaMnO3.

Author

Kharlamova, M. V. and Arulraj, A.

Subjects
*LANTHANUM, *MANGANESE, *NANOCRYSTALS, *PRECIPITATION (Chemistry), *SOLUTION (Chemistry), *ANNEALING of metals, *X-ray diffraction, *NEUTRON diffraction
Abstract

Nanocrystalline LaMnO3 samples have been synthesized by the coprecipitation of lanthanum and manganese salt solutions followed by annealing at 800°C in air and then in an argon flow. With the use of X-ray and neutron diffraction analysis, it has been found that the resulting samples had an orthorhombic crystal structure (space group Pbnm). In the nanocrystalline LaMnO3 samples, an order-disorder phase transition from the low-temperature phase to the high-temperature phase occurs at (220 ± 10)°C, which is much lower than the value of 477°C for bulk LaMnO3. The phase transition is due to the removal of the Jahn-Teller distortion of the Mn3+O6 oxygen octahedrons and is accompanied by a decrease in the unit cell volume of lanthanum manganite over a narrow temperature range. [ABSTRACT FROM AUTHOR]

Published
2009
Full Text
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34. Phase transition in nanostructured LaMnO3.

Author

Kharlamova, M. V. and Arulraj, A.

Subjects
LANTHANUM, MANGANESE, NANOCRYSTALS, PRECIPITATION (Chemistry), SOLUTION (Chemistry), ANNEALING of metals, X-ray diffraction, NEUTRON diffraction
Abstract

Nanocrystalline LaMnO3 samples have been synthesized by the coprecipitation of lanthanum and manganese salt solutions followed by annealing at 800°C in air and then in an argon flow. With the use of X-ray and neutron diffraction analysis, it has been found that the resulting samples had an orthorhombic crystal structure (space group Pbnm). In the nanocrystalline LaMnO3 samples, an order-disorder phase transition from the low-temperature phase to the high-temperature phase occurs at (220 ± 10)°C, which is much lower than the value of 477°C for bulk LaMnO3. The phase transition is due to the removal of the Jahn-Teller distortion of the Mn3+O6 oxygen octahedrons and is accompanied by a decrease in the unit cell volume of lanthanum manganite over a narrow temperature range. [ABSTRACT FROM AUTHOR]

Published
2009
Full Text
View/download PDF

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