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首页> 外文期刊>Solid State Communications >Synthesis, structural and transport properties of nanocrystalline La_(1-x)Ba_xMnO_3 (0.0 ≤ x ≤ 0.3) powders
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Synthesis, structural and transport properties of nanocrystalline La_(1-x)Ba_xMnO_3 (0.0 ≤ x ≤ 0.3) powders

机译：纳米La_（1-x）Ba_xMnO_3（0.0≤x≤0.3）粉末的合成，结构和传输性能

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摘要

Nanocrystalline La_(1-x)Ba_xMnO_3 (0.0 ≤ x ≤ 0.3) manganites have been prepared by a simple and instantaneous solution combustion method, which is a low temperature initiated synthetic route to obtain fine-grained powders with relatively high surface area. The phase purity and crystal structure of the combustion products are carried out by powder X-ray diffraction. The as-made nanopowders are in cubic phase. On calcination to 900 ℃, barium doped manganites retain cubic phase, whereas barium free manganite transformed to rhombohedral phase. The scanning electron microscope (SEM) results revealed that the combustion-derived compounds are agglomerated with fine primary particles. The doped manganites have surface area in the range 24-44 m~2/g. The surface area of the manganites increases with barium content, whereas it decreases on calcination. Both undoped and doped lanthanum manganites show two active IR vibrational modes at 400 and 600 cm~(-1). The low temperature resistivity measurements have been carried out by four-probe method down to 77 K. All the samples exhibit metal-insulator behaviour and metal-insulator transition temperature (T_(M-I)) in the range 184—228 K and it is interesting to note that, as the barium content increases the T_(M-I) shifts to lower temperature side. The maximum T_(M-I) of 228 K is observed for La_(0.9)Ba_(0.1)MnO_3 sample.
机译：纳米晶La_（1-x）Ba_xMnO_3（0.0≤x≤0.3）锰矿是通过简单且瞬时的固溶燃烧方法制备的，该方法是低温引发的合成路线，以获得具有较高表面积的细粉。燃烧产物的相纯度和晶体结构通过粉末X射线衍射进行。制成的纳米粉处于立方相。煅烧至900℃时，掺杂钡的锰矿保留立方相，而不含钡的锰矿转变为菱面体相。扫描电子显微镜（SEM）结果表明，燃烧衍生的化合物与细小的初级颗粒团聚。掺杂的锰矿的表面积为24-44m〜2 / g。锰的表面积随钡含量的增加而增加，而在煅烧时减少。未掺杂和掺杂的镧锰矿在400和600 cm〜（-1）处均表现出两种活跃的IR振动模式。低温电阻率测量是通过四探针法进行的，直到77K。所有样品的金属-绝缘体行为和金属-绝缘体转变温度（T_（MI））都在184-228 K范围内，这很有趣需要注意的是，随着钡含量的增加，T_（MI）移至较低温度侧。对于La_（0.9）Ba_（0.1）MnO_3样品观察到最大228 K的T_（M-1）。

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