LiZn铁氧体电磁性能研究
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摘要
LiZn铁氧体由于具有矩形磁滞回线、高居里温度、剩磁对应力敏感性低等特点,被广泛应用于微波器件中。本文重点研究缺铁配方、添加剂及制备工艺对LiZn铁氧体电磁性能的影响,以探索低温制备低损耗LiZn铁氧体材料的有效途径。
首先,采用氧化物工艺研究了添加剂、缺铁配方及烧结工艺对LiZn铁氧体电磁性能的影响。结果表明:Bi2O3添加剂在烧结过程中形成液相烧结,能有效地降低材料的烧结温度,促进铁氧体的烧结致密化和晶粒生长,提高材料的电磁性能;在烧结过程中,Mn3O4的加入能有效抑制材料中Fe2+的存在,提高材料的电阻率,并改善了材料的磁性能;Nb2O5能细化晶粒,改善材料的微观结构,从而提高LiZn铁氧体的电阻率,降低微波介电损耗;适当的缺铁量能有效改善材料的微结构,同时提高材料的饱和磁化强度及剩磁比,降低矫顽力与9.2GHz频率下的铁磁共振线宽及介电损耗;而适宜的烧结温度能使晶粒生长均匀,气孔减小,有效地提高材料的性能;其次,利用溶胶-凝胶柠檬酸自蔓延工艺制备了LiZn铁氧体纳米粉体,研究了柠檬酸组分、成胶温度等工艺条件对纳米粉体性能与形貌的影响;并结合氧化物工艺研究了助熔剂、缺铁配方与烧结工艺对LiZn铁氧体的烧结样品电磁性能的影响。结果表明:增加柠檬酸用量,纳米粉体的比饱和磁化强度和粒径均减小;降低成胶温度有利于溶胶形成结构稳定的凝胶网络,从而提高纳米粉体的比饱和磁化强度,改善烧结体的微结构,并提高LiZn铁氧体的饱和磁化强度和降低矫顽力;Bi2O3添加剂能够降低材料的烧结温度,提高材料的电磁性能;适宜的缺铁配方能有效改善材料的电磁性能,并能在较低的烧结温度条件下得到性能优异的LiZn铁氧体材料。
LiZn ferrites are widely uesed in microwave devices due to their rectangular hysteresis loop、high curie temperature and low stress sensitivity of remanent magnetic induction.The effects of iron-deficient composition, additives and sintering-process on the electromagnetic properties of the low-dielectric loss LiZn ferrites were studied in this paper. As a result, the low dielectric loss LiZn ferrites were synthesized successfully at low sintering temperature.
First, the effects of iron-deficient composition, additives and sintering-process on the electromagnetic properties of the LiZn ferrite prepared by conventional ceramic process were studied. The results showed that the addition of Bi2O3 can improve the densification behavior and grain growth, decrease the sintering-temperature and improve electromagnetic properties of LiZn ferrite, owing to a liquid phase sintering occurs during the sintering process. The addition of Mn3O4 can effectively restrains the appearance of Fe2+ ions during sintering process, improve the resistivity and magnetic properties of LiZn ferrite. Nb2O5 can refine grain size and improve the microstructure which then improve the resistivity and reduce the microwave dielectric loss of LiZn ferrite. Then the effects of iron deficiency on the microstructure and electromagnetic properties of LiZn ferrite were investigated. The results indicated that optimum iron deficiency can reduce the ferromagnetic resonance line-width and dielectric loss at 9.2GHz, enhance saturation and squareness ratio, and decrease coercive force. Optimum sintering parameters are beneficial to produce uniform grain structure and decrease the porosity, which then attributes to improve the properties of materials. Secondly, we successfully synthesized the series of nanometer powder of the LiZn ferrite by Sol-Gel citric acid self-propagating method, studied the influence of the rate of citric and the gelation temperature, And combined with conventional ceramic process, the effects of flux, iron deficiency and sintering process on electromagnetic properties of LiZn ferrite were investigated. The results showed that with the increase of citric acid, both the diameter of the power particle and specific saturation magnetization decrease. While bringing down the gelation temperature is beneficial to the formation of stable gel network which then enhances the specific saturation magnetization of nano-powder, improves the microstructure of singtering samples, increase the sturation magnetization and decreases the coercive force of LiZn ferrite. Bi2O3 could decrease the sintering-temperature and improve electromagnetic properties of LiZn ferrite. Optimum iron deficiency could improve the electromagnetic properties of LiZn ferrite and help to obtain LiZn ferrite with better properties at lower sintering temperature.
首先,采用氧化物工艺研究了添加剂、缺铁配方及烧结工艺对LiZn铁氧体电磁性能的影响。结果表明:Bi2O3添加剂在烧结过程中形成液相烧结,能有效地降低材料的烧结温度,促进铁氧体的烧结致密化和晶粒生长,提高材料的电磁性能;在烧结过程中,Mn3O4的加入能有效抑制材料中Fe2+的存在,提高材料的电阻率,并改善了材料的磁性能;Nb2O5能细化晶粒,改善材料的微观结构,从而提高LiZn铁氧体的电阻率,降低微波介电损耗;适当的缺铁量能有效改善材料的微结构,同时提高材料的饱和磁化强度及剩磁比,降低矫顽力与9.2GHz频率下的铁磁共振线宽及介电损耗;而适宜的烧结温度能使晶粒生长均匀,气孔减小,有效地提高材料的性能;其次,利用溶胶-凝胶柠檬酸自蔓延工艺制备了LiZn铁氧体纳米粉体,研究了柠檬酸组分、成胶温度等工艺条件对纳米粉体性能与形貌的影响;并结合氧化物工艺研究了助熔剂、缺铁配方与烧结工艺对LiZn铁氧体的烧结样品电磁性能的影响。结果表明:增加柠檬酸用量,纳米粉体的比饱和磁化强度和粒径均减小;降低成胶温度有利于溶胶形成结构稳定的凝胶网络,从而提高纳米粉体的比饱和磁化强度,改善烧结体的微结构,并提高LiZn铁氧体的饱和磁化强度和降低矫顽力;Bi2O3添加剂能够降低材料的烧结温度,提高材料的电磁性能;适宜的缺铁配方能有效改善材料的电磁性能,并能在较低的烧结温度条件下得到性能优异的LiZn铁氧体材料。
LiZn ferrites are widely uesed in microwave devices due to their rectangular hysteresis loop、high curie temperature and low stress sensitivity of remanent magnetic induction.The effects of iron-deficient composition, additives and sintering-process on the electromagnetic properties of the low-dielectric loss LiZn ferrites were studied in this paper. As a result, the low dielectric loss LiZn ferrites were synthesized successfully at low sintering temperature.
First, the effects of iron-deficient composition, additives and sintering-process on the electromagnetic properties of the LiZn ferrite prepared by conventional ceramic process were studied. The results showed that the addition of Bi2O3 can improve the densification behavior and grain growth, decrease the sintering-temperature and improve electromagnetic properties of LiZn ferrite, owing to a liquid phase sintering occurs during the sintering process. The addition of Mn3O4 can effectively restrains the appearance of Fe2+ ions during sintering process, improve the resistivity and magnetic properties of LiZn ferrite. Nb2O5 can refine grain size and improve the microstructure which then improve the resistivity and reduce the microwave dielectric loss of LiZn ferrite. Then the effects of iron deficiency on the microstructure and electromagnetic properties of LiZn ferrite were investigated. The results indicated that optimum iron deficiency can reduce the ferromagnetic resonance line-width and dielectric loss at 9.2GHz, enhance saturation and squareness ratio, and decrease coercive force. Optimum sintering parameters are beneficial to produce uniform grain structure and decrease the porosity, which then attributes to improve the properties of materials. Secondly, we successfully synthesized the series of nanometer powder of the LiZn ferrite by Sol-Gel citric acid self-propagating method, studied the influence of the rate of citric and the gelation temperature, And combined with conventional ceramic process, the effects of flux, iron deficiency and sintering process on electromagnetic properties of LiZn ferrite were investigated. The results showed that with the increase of citric acid, both the diameter of the power particle and specific saturation magnetization decrease. While bringing down the gelation temperature is beneficial to the formation of stable gel network which then enhances the specific saturation magnetization of nano-powder, improves the microstructure of singtering samples, increase the sturation magnetization and decreases the coercive force of LiZn ferrite. Bi2O3 could decrease the sintering-temperature and improve electromagnetic properties of LiZn ferrite. Optimum iron deficiency could improve the electromagnetic properties of LiZn ferrite and help to obtain LiZn ferrite with better properties at lower sintering temperature.
引文
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[2]韩志全.微波铁氧体材料的发展概况.磁性材料及器件, 2000, 31(5):32-35
[3] EMS公司产品目录, 2006
[4] P. D. Baba. Fabrication and properties of microwave lithium ferrites. IEEE Trans. Magn., 1972, mag-8(1):83-93
[5]王会宗. Li-Mg-Ti铁氧体的研究.电子学报, 1979, 11(1):64-70
[6] S. H. Gee, Y. K. Hong, M. H. Park, et al. Synthesis of nanosized (Li0.5xFe0.5xZn1-x)Fe2O4 particles and magnetic properties. J. Appl. Phys., 2002, 91,(10):7586-7587
[7]韩志全,廖杨,冯涛.氧化物法低温烧结Li系铁氧体的固相反应、致密化过程及微波性能.磁性材料及器件, 2007, 38(2):23-25
[8]李俊蓉,李文兵,王会宗.溶胶-凝胶法制备纳米LiZn铁氧体的磁性能.磁性材料及器件, 2004, 36(3):30-32
[9] Z. X. Yue, J. Zhou, X. H. Wang, et al. Preparation and magnetic properties of titanium-substituted LiZn ferrites via a sol-gel auto-combustion process. J. Europ. Ceram. Soc., 2003 , 23:189-193
[10]韩志全,廖杨,冯涛.Sol-Gel法低温共烧LiZn铁氧体研究.磁性材料及器件, 2007, 38(3):16-19
[11] E. Rezlescu, N. Rezlescu. Densification by nonmagnetic additives of high frequence LiZn and NiZn ferrites. J. Magn. Magn. Mater., 2003, 157:487-488
[12]荆玉兰.复合添加对锂铁氧体烧结特性和电磁性能的影响.磁性材料及器件, 2005, 10(5):44-46
[13] M. P. Bunina, E. V. Lebedeva, A. I. Pil’shchikov, et al. Effectiveness of the influence of Co2+ on spinwave losses. Fiz. Tverd. Tela., 1970, 12:433-438
[14]黄永杰,李世堃,兰中文.磁性材料.成都:电子科技大学出版社, 1994, 1-100
[15]宛德福,马兴隆.磁性物理学.成都:电子科技大学出版社, 1994, 1-484
[16]张国荣.微波铁氧体材料与器件.北京:电子工业出版社, 1995, 1-60
[17]蒋仁培,魏克珠.微波铁氧体理论与技术.北京:科学出版社, 1984, 44-75
[18] Tetsuji Inui, Naoyuki Ogasawara. Grain-size effects on microwave ferrite magnetic properties. IEEE Trans Magn, 1977, Mag-4(13):1729-1744.
[19]都有为.铁氧体.江苏:科学技术出版社, 1996, 4-338
[20] A. J. Pointon and R.C. Saull J. Solid state reactions in lithium territe. Ameri. Cera. Soci. 1969, 52(3):157-160
[21] D. H. Ridgley. H. Lessoff. Effects of lithium and oxygen losses on magnetic and crystallographic properties of spinel lithium ferrite. J. Amer. Ceram. Soc., 1970, 53:304-311
[22]李标荣.电子陶瓷工艺原理.武汉:华中工学院出版社, 1986, 59-142
[23] C. Y. Liu, Z. W. Lan, X. N. Jiang, et al. Effects of sintering temperature and Bi2O3 content on microstructure and magnetic properties of LiZn ferrites. J. Magn. Magn. Mater., 2008, 320:1335-1339
[24] H. T. Kim, H. B. Im. Effects of Bi2O3 and Nd2O5 on the magnetic properties on Ni-Zn ferrites and Lithium ferrites. IEEE Trans. Magn., 1982, mag-18(6):1541-1543
[25] S. F. Wang, Y. R. Wang, C. K. Yang, et al. Densification and properties of fluxed sintered NiCuZn ferrites. J. Magn. Magn. Mater., 2000, 217:35-43
[26] L. J. Jia, H. W. Zhang, Y. L. Liu, et al. Effects of mixing procedure and Bi2O3 content on structural and magnetic properties of hexaferrites sintered at low temperature. J. Magn. Magn. Mater., 2007, 316:67-72
[27] Z. Yu, K. Sun, L. Z. Li, et al. Influences of Bi2O3 on microstructure and magnetic properties of MnZn ferrite. J. Magn. Magn. Mater., In press.
[28]余忠,兰中文.液相烧结制备高密度R5K MnZn铁氧体磁头材料.材料导报, 2004, 18(3):85-87
[29]余忠,陈代中,兰忠文,等. Bi2O3对烧结LiZn铁氧体性能的影响.无机材料学报, 2007, 22(6):1173-1177
[30] G. O. White, C. E. Patton. Magnetic properties of lithium ferrite microwave materials. J. Magn. Magn. Mater., 1978, 9:299-317
[31] Sh. Sh. Bashkirov, R.A. Iskhakov, A. B. Liberman, et al. Influence of manganese and gallium ions on the magnetic structure of lithium ferrites. Russian Physics Journal., 1975, 18:1715-1717
[32]周志刚.铁氧体磁性材料.北京:科学出版社, 1978, 329-342
[33]张益栋,兰忠文,余忠. Nb2O5掺杂对高频MnZn功率铁氧体微结构和性能的影响.磁性材料及器件, 2003, 38(5):8-10
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