La0．8Ba0．2Mn1-yCuyO3的微波吸收性能

用溶胶-凝胶法制备了La0．8Ba0．2Mn1-yCuyO3系列微粉,测量了部分样品在2～18GHz范围的复介电常数和复磁导率并根据测量数据计算出材料的微波反射率,结果表明La0．8Ba0．2Mn1-yCuyO3系列具有较好的微波吸收性能,当y为0．13时,1．8mm厚时的最大吸收峰值达到28dB,10dB以上的吸收带宽达到3．1GHz;当y为0．17时,1．8mm厚时的最大吸收峰值达到29db,10dB122＆的吸收带宽达到2．5GHz。电磁频谱分析表明La0．8Ba0．2Mn1-yCuyO3以介电损耗为主,同时具有一定的磁损耗。     

纳米La0．8Ba0．2MnO3／Ni粉复合体系的微波吸收性能

采用溶胶-=凝胶法制备La0．8Ba0．2MnO3粉体,并与纳米Ni粉按不同质量比复合,制得复合材料样品。测量样品在2-18GHz频率范围内的复介电常数、复磁导率并计算微波反射系数,分析不同组分对材料微波吸收性能的影响及其可能的吸收机制。研究结果表明：复合体系比单一组分样品具有更好的吸收效果;当La0．8Ba0．2MnO3含量为62、5％时,材料微波吸收效果最佳;当样品厚度为2mm时,大于10dB的吸收频宽达到3．6GHz,最大吸收峰值为24dB;当样品厚度为1．8mm时,大于10dB的吸收频宽达到3．3GHz,最大吸收峰值为44dB;LaMnO,在A位掺杂Ba2＋,其电磁性能将发生变化,再与磁性纳米Ni粉复合,介电损耗和磁损耗的综合作用能使体系的微波吸收效能显著加强。     

Microwave absorbing properties of La0.8Ba0.2MnO3 nano-particles

La0.8Ba0.2MnO3 nano-particles were synthesized by sol-gel process, and the crystal structure and morphology＇ were characterized by XRD and SEM, respectively. The complex permittivity and permeability were determined by microwave vector network analyzer in the frequency range of 2-18 GHz. The relationship between reflection coefficient and microwave frequency of La0.8Ba0.2 MnO3 was calculated based on measured data. The results show that the average diameter of La0.8Ba0.2MnO3 crystal powders is about 80 nm and the crystal structure is perovskite when being calcined at 800 ℃ for 2 h. The microwave absorbing peak is 13 dB at 6.7 GHz and the effective absorbing bandwidth above 10 dB reaches 1.8 GHz for the sample with the thickness of 2.6 mm. The microwave absorption can be attributed to both the dielectric loss and the magnetic loss from the loss tangents of the sample, but the former is greater than the latter.     

La0．8Ba0．2MnO3纳米晶的制备与表征

用溶胶-凝胶法制备了La0.8Ba0.2MnO3纳米粉体材料,对样品的凝胶进行热差热熏和红外光谱分析,结果表明,凝胶的加热煅烧过程中可以分为脱吸附水、有机物分解、硝酸根分解和钙态矿形成四个阶段。X射线衍射分析表明它是单一的钙态矿结构,扫描电子显微镜分析表明粉体呈球形巍径约80nm。     

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