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摘要钙钛矿结构的ReFeO3（Re代表稀土）是一类重要的材料，具有铁磁、磁光等优良性质。他们在燃料电池、催化剂、气敏材料、半导体材料、磁光材料等领域有着广泛的应用。在RFeO3体系中，NdFeO3具有自旋重取向、气敏等特点，具有潜在的应用前景。我们在制备与磁性能方面的研究将有益于它将来在是实际中的应用。[3] 29936
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本实验通过优化工艺，采用溶胶-凝胶自蔓延燃烧法制备了一系列正交钙钛矿结构的Mn掺杂NdFeO3粉体。结合XRD、TEM、VSM等手段，详细分析了Mn掺杂对于NdFeO3的结构、形貌和磁性能的影响规律。当CA/MN=1，热处理温度高达1000℃，NdFeO3中仍存在Nd2O3杂质，而当CA/MN=1.5时，热处理温度仅为800℃，即可以得到纯相的NdFeO3。对于Mn掺杂NdFeO3样品，当CA/MN=1时，热处理为900℃时，得到纯相NdFe0.9Mn0.1O3，但是随着掺杂浓度的提高，Nd2O3杂质含量越高。当CA/MN=1.5时，热处理温度仅为800℃，完全正交钙钛矿结构的NdFe1-xMnxO3 (x≤0.3) 即可得到。并且随着煅烧温度不断升高，衍射强度不断增强，样品的结晶程度在不断加强。通过以上分析可知，在CA/MN=1.5时，更利于正交钙钛矿NdFeO3相的形成。这可能是由于当CA/MN=1.5时，柠檬酸量充分，在自燃过程中，能够发生更充分的氧化还原反应，因此能够在较低的温度下，得到完全纯相的NdFeO3粉体。
未掺杂NdFeO3粉体在室温下表现出铁磁性，并伴随有反铁磁性。当Mn掺杂之后，样品的磁化强度明显降低，铁磁性也明显减弱，反铁磁性增强，这主要是由于Mn3+较小的磁矩，以及掺杂造成结构畸变造成的。
毕业论文关键词： NdFeO3；磁性；掺杂
Abstract
ReFeO3 (Re) of perovskite structure is a kind of important material, and has good properties such as ferromagnetic, magnetic light and so on.. They are widely used in fuel cell, catalyst, gas sensitive material, semiconductor material, magnetic material and so on.. In the RFeO3 system, NdFeO3 has the characteristics of the spin weight orientation, gas sensitivity, etc., and has potential applications. The research on the preparation and magnetic properties will benefit the application of it in the future.
In this experiment, a series of transition metal doped NdFeO3 powders with orthorhombic perovskite structure were prepared by sol-gel combustion method. The effect of Mn doping on the structure, morphology and magnetic properties of NdFeO3 was analyzed by means of VSM, TEM and XRD. When CA/MN=1, the heat treatment temperature reached 1000 degrees, main NdFeO3 phase was obtained, with Nd2O3 impurities. Under the condition of CA/MN=1.5, pure phase NdFeO3 was obtained when annealed at 800℃. For Mn doped NdFeO3 samples, with CA/MN=1, pure phase NdFe0.9Mn0.1O3 was obtained when annealed at 900℃. With increasing doping concentration of Mn, the content of Nd2O3 impurity is higher. When CA/MN=1.5, completely pure phase of NdFe1-xMnxO3 was readily formed at 800℃. The results show that pure phase NdFe1-xMnxO3 (x≤0.3) is more easily formed when CA/MN=1.5.
Undoped NdFeO3 powders showed ferromagnetic behavior at room temperature, with coexisting antiferromagnetic behavior. The magnetization of the sample significantly decreased after Mn doping. The ferromagnetism was significantly decreased, while the antiferromagnetic coupling is enhanced. This is mainly caused due to smaller magnetic moments of Mn3+, as well as structure distortion caused by the doping of Mn.
KeyWords: NdFeO3; Magnetic propery; Doping
目 录
1 文献综述 1
1.1 ReFeO3晶体结构 1
1.2 ReFeO3晶体的性能 2
1.2.1 ReFeO3晶体的磁性能 2
1.2.2NdFeO3晶体的磁性能 3
1.2.3 ReFeO3晶体的磁光性能 4
1.2.4 NdFeO3晶体的气敏性能 6