Magnetism and magnetocaloric effect in nanocrystalline La0.67Ca0.33Mn0.9V0.1O3 synthesized by nebulized spray pyrolysis
Magnetism and magnetocaloric effect in nanocrystalline La0.67Ca0.33Mn0.9V0.1O3 synthesized by nebulized spray pyrolysis
复制标题
DOI：
10.1088/0022-3727/43/13/135001
复制
发表时间：
2010-04
期刊：
影响因子：
--
通讯作者：
P. Nisha;S. S. Pillai-S.;A. Darbandi;A. Misra;K. G. Suresh;Manoj Raama Varma;H. Hahn
中科院分区：
文献类型：
--
作者：
P. Nisha;S. S. Pillai-S.;A. Darbandi;A. Misra;K. G. Suresh;Manoj Raama Varma;H. Hahn
使用雾化喷雾热解合成了纳米晶形式的钒 (V) 取代的 La0.67Ca0.33MnO3。透射电子显微镜研究表明，制备了平均尺寸在 30-40 nm 范围内的高度均匀的纳米颗粒。 XRD 图谱的 Rietveld 精修表明样品采用具有 Pnma 空间群的斜方结构。与纳米晶La0.67Ca0.33MnO3 (TC = 260 K)相比，晶格参数和磁相变(TC = 252 K)的系统变化表明了V的替代效应。在一定温度范围内的M-H曲线反映了样品的超顺磁性。从 Langevin 拟合获得的超顺磁簇的平均粒径（~28 nm）与高分辨率透射电子显微镜图像显示的纳米晶簇的平均粒径一致。阿罗特图揭示了样品磁相变的一级特征。对于252 K、5 T的磁场，这些纳米粉末的峰值磁熵变（ΔSmax）估计约为4.5 J kg−1 K−1。与块状La0.67Ca0.33Mn0.9V0.1O3相比，纳米颗粒的熵变较小，但熵变发生在较宽的温度范围内，从而产生较大的相对冷却能力。
Vanadium (V) substituted La0.67Ca0.33MnO3 was synthesized in the nanocrystalline form using nebulized spray pyrolysis. Highly uniform nanoparticles of average size in the range 30–40 nm as revealed by transmission electron microscopic studies were prepared. Rietveld refinement of XRD patterns shows that the sample adopts an orthorhombic structure with the Pnma space group. The systematic change in lattice parameters and magnetic phase transition (TC = 252 K) as compared with those of nanocrystalline La0.67Ca0.33MnO3 (TC = 260 K) indicate the substitutional effect of V. M–H curves in a certain temperature range reflect the superparamagnetic nature of the sample. The average particle size (∼28 nm) of the superparamagnetic clusters obtained from the Langevin fit is coincident with that of the nanocrystalline clusters revealed by the high-resolution transmission electron microscopy images. The Arrott plots reveal the first order character of magnetic phase transition of the sample. The peak magnetic entropy change (ΔSmax) of these nanopowders is estimated to be about 4.5 J kg−1 K−1 for a magnetic field of 5 T at 252 K. Compared with the bulk La0.67Ca0.33Mn0.9V0.1O3, the entropy change of the nanoparticles is found to be smaller, but the entropy change occurs over a broad temperature range, giving rise to a large relative cooling power.