La_(1-x)Ce_xMnO_3凝胶晶化过程与微波吸收性能

The Gel Crystallization Process and Microwave Absorption Properties of La_(1-x)Ce_xMnO_3

用溶胶—凝胶法制备了La1-xCex MnO3粉体,根据DSC-TGA、FT-IR、XRD分析了样品的晶化过程,用圆柱体法测试了样品的室温电阻率,用微波网络分析仪测试样品的微波吸收性能.结果表明,样品凝胶在煅烧时经过脱水、剧烈分解、逐渐晶化等过程,900℃左右形成稳定的钙钛矿结构并伴有少量CeO2杂相;室温电阻率处于半导体范围,且随掺杂量x增加而减小;样品厚度为2.2 mm、x=0.4时,13.2 GHz频率位置处微波吸收峰值为27 dB,10 dB频宽为3.2 GHz.分析认为,合适的电阻率、钙钛矿晶体极化驰豫及共振、铁磁团簇转向及共振是材料具有良好微波吸收性能的原因.

The powder samples of La1-xCexMnO3 were prepared by sol-gel method and their crystallization process was discussed on the basis of DSC-TGA, XRD and FT-IR. Their con- ductivities at room temperature and microwave absorption properties were measured respec- tively by cylinder method and microwave network analyzer. The results show that the gel of La1-xCexMnO3 went through dehydration, severe decomposition and gradual crystallization and transformed into a stable perovskite structure with a small amount of CeO2 impurity phase about 900℃ when calcined. The resistivites of the samples were within semicon- ductor area and reduced with Ce content x increase. The effective absorption bandwidth a- bove 10 dB for La1-xCexMnO3 was 3.2 GHz and the absorption peak was 27dB at 13.2 GHz when the thickness was 2.2 mm and x = 0.4. From the analysis,it is believed that La1-xCexMnO3 has excellent microwave absorption because of appropriate resistivity, polarization relaxation and resonance of perovskite crystal, and turning and resonance of ferromagnetic clusters in the sample under microwave electromagnetic field.