Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxiclic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size < 30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures.
Structural and magnetic properties of pure and Ca-doped LaCoO3 nanopowders obtained by a sol-gel route / L. ARMELAO; D. BARRECA; G. BOTTARO; A. CANESCHI; C. SANGREGORIO; ; S. GIALANELLA; C. MARAGNO; E. TONDELLO. - In: JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY. - ISSN 1533-4880. - STAMPA. - 6:(2006), pp. 1060-1067. [10.1166/jnn.2006.147]
Structural and magnetic properties of pure and Ca-doped LaCoO3 nanopowders obtained by a sol-gel route
CANESCHI, ANDREA;
2006
Abstract
Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxiclic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size < 30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.