烧结温度和升温速率对铁氧体粉体粒径的影响

采用柠檬酸盐溶胶-凝胶法制备尖晶石型铁氧体粉体,通过扫描电子显微镜和粒度分析仪表征产物的粒径大小,研究烧结温度和升温速率对铁氧体粒径的影响。结果表明:多步升温的方式更有利于形成粒径小且均匀的铁氧体粉体,得到的产物粒径约为300 nm;随着烧结温度的升高,铁氧体颗粒的粒径呈先减小后增大的趋势,850℃为最佳烧结温度,适用于制备颗粒均匀、粒径小的尖晶石型铁氧体粉体。     

烧结对共沉淀预烧料制备MnZn高导铁氧体磁性能的影响

以共沉淀法预烧粉为原料,研究了烧结温度及烧结气氛对MnZn高导铁氧体磁性能的影响,采用SEM对其微观结构进行了表征。结果表明,随着烧结温度升高,MnZn高导铁氧体的μi增加;合适的烧结条件能促进晶粒生长,减少气孔产生,增大烧结密度,使晶界变细,提高初始磁导率和改善频率特性。当温度为1380℃,保温气氛为3.0%时,MnZn高导铁氧体的μi为13000,且有较好的频率特性,在150kHz时μi能维持在10000以上。     

预烧温度对MnZn功率铁氧体烧结活性及温度稳定性的影响

采用氧化物陶瓷工艺制备了MnZn功率铁氧体.研究了预烧温度对MnZn功率铁氧体烧结活性及磁性能、温度稳定性的影响.结果表明,MnZn功率铁氧体预烧料粉体的活性随预烧温度的升高而降低.预烧料粉体的活性对其烧结样品的微观结构有很大影响.预烧温度在870℃时样品具有最佳的磁性能和温度稳定性.     

工艺条件对MnZn功率铁氧体性能的影响

研究了粉末体粒度、成型密度和烧结工艺对ＭｎＺｎ功率铁氧体材料性能的影响，指出了组成为Ｚｎ０．１６Ｍｎ０．７６Ｆｅ２．０８Ｏ４的材料的最佳工艺条件，得到了与日本ＴＤＫ公司ＰＣ５０材料性能相的的功率铁氧体。     

烧结氧分压对二次料制备的MnZn铁氧体性能的影响

利用电磁炉生产过程中产生的MnZn铁氧体废料,研究了烧结气氛中的氧分压对以二次料为原料采用传统陶瓷法制备的MnZn铁氧体。利用多种表征手段,对MnZn铁氧体的的物相构成和微观结构进行表征,进而研究了氧分压对MnZn铁氧体的微观形貌和软磁性能的影响。结果表明,适当的氧分压可以改善组织。随着氧分压从8%减小至1%时,振幅磁导率先增大而后减小,矫顽力和比总损耗则先减小而后增大。当氧分压为3%时,样品具有单一的尖晶石型MnZn铁氧体相、较好的微观组织和最佳的软磁性能。在100mT和25kHz条件下测得的振幅磁导率、矫顽力和比总损耗分别为2970、11.6A/m和15.6W/kg。     

Ti取代对MnZn功率铁氧体微结构及磁性能的影响

采用氧化物陶瓷工艺制备了MnZn功率铁氧体,研究亮磁性能的影响,由于Ti4 是非磁性离子,它对磁性离子Mn2 的取代,必将对材料的微结构、磁性能以及居里温度产生影响.结果表明,Ti4 取代Mn2 可提高MnZn铁氧体居里温度,适量的Ti4 取代,有利于提高致密度和起始磁导率,并降低磁损耗.为了得到优良的电磁性能,适宜的Ti4 取代量为0.5mol%.     

掺杂对功率铁氧体磁性能的影响

研究了不同的掺杂组合对MnZn功率铁氧体磁性能的影响。并与传统的最常用的CaO-SiO2做了比较。我们还发现Ca、Ta和Nb离子作为一组掺杂,组以适配的工艺条件,可以取得比常用的CaO—SiO2更好的结果。     

SnO2掺杂对MnZn铁氧体微观结构和性能的影响

采用氧化物陶瓷工艺制备MnZn功率铁氧体,研究了SnO2掺杂对MnZn功率铁氧体微观结构及磁性能的影响。结果表明添加适量的SnO2可以有效提高晶粒均匀性和致密度。随着SnO2添加量的增加,起始磁导率先上升后下降,磁损耗先下降后上升。当添加量为0.5%(摩尔分数)时,μi达到最大值,损耗最低。此外,铁氧体损耗最低点所对应的温度随着SnO2掺杂量的增加向低温移动。通过对比一次掺杂和二次掺杂,发现一次掺杂的SnO2主要作用于晶粒内部,二次掺杂的SnO2主要作用于晶界处,而且一次掺杂所获得的样品性能更优。     

掺CaO-B2O3-SiO2玻璃烧结制备MnZn铁氧体及其磁性能

采用传统陶瓷工艺制备了CaO-B2O3-SiO2(CBS)玻璃掺杂的MnZn铁氧体.研究了CBS玻璃掺入量及烧结温度对MnZn铁氧体的烧结特性及磁性能的影响.结果表明:样品的密度随着CBS掺入量的增加而不断减小,磁性能随着温度的升高而不断增强;掺入适量CBS可在烧结时形成液相,使固体颗粒间产生液相烧结并促进晶粒的长大....     

液相烧结制备高密度R5K MnZn铁氧体磁头材料

低熔点氧化物添加剂在烧结时形成液相,可促进MnZn铁氧体磁头材料致密化,提高密度,改善磁性能.采用液相烧结,制备了组成为Mn0.60Zn0.32Fe2.08O4的高密度MnZn铁氧体磁头材料.     

Pressure sintering of MnZn and NiZn ferrites

Polycrystalline MnZn and NiZn ferrites suitable for recording-head applications have been prepared by pressure sintering (hotpressing). General conditions for pressure sintering and details of the apparatus are described. Also discussed are the effects of grain size and temperature, in the normal range of glass bonding, on the magnetic and physical properties of pressure-sintered MnZn ferrite. It was observed that the strength of the ferrite increased with decreasing grain size in the range studied (15 to 500 μm). An opposite effect was noted for resistance to material wear. Increases in permeability up to 30 percent were obtained by relieving residual machining stresses with anneals in the 500 to 900°C range. Similar increases in strength were observed for low-temperature anneals. However, at temperatures higher than 500°C, the strength was reduced strongly, with the amount of the reduction being dependent upon the surface finish of the ferrite and its geometry. In general, strength was reduced with coarser surface finish and increasing surface-to-volume ratios. Data on material wear and hardness as functions of grain size and composition are presented. Improvement in performance of video recording heads fabricated of pressure-sintered MnZn ferrite as compared to Alfesil and single-crystal MnZn ferrite is also demonstrated.     

Effect of dopants on the magnetic properties of MnZn ferrites forhigh frequency power supplies

The effect of additions on the magnetic properties of MnZn ferrites for high frequency power supplies was studied. The investigation revealed that various combinations of dopants added to the ferrite modify the grain boundary resistivity and the magnetic permeability spectra at constant microstructure. Particularly, the combined effect of Sn⁴⁺, Ti⁴⁺ and Ta⁵⁺ was found to increase the grain boundary resistivity in the ferrites studied and remarkably decrease the power loss at higher frequencies     

Effects of calcining and sintering parameters on the magnetic properties of high-permeability MnZn ferrites

For asymmetric digital subscriber line (ADSL) technology applications, new MnZn ferrites are required with not only high initial permeability, but also with low hysteresis material constant /spl eta//sub B/. The effects of calcining and sintering temperatures and oxygen equilibrium partial pressure on the magnetic properties of MnZn ferrites are studied in this work. It was found that raising the calcining temperature required a rise in the sintering temperature to simultaneously achieve maximum permeability and the lowest /spl eta//sub B/ value. Both grain size and porosity had an effect on the initial permeability of the samples. Porosity had an even larger effect on the /spl eta//sub B/ value than the initial permeability. Oxygen equilibrium partial pressure also had an important effect on the initial permeability and /spl eta//sub B/ value. In our testing range, both the initial permeability and the /spl eta//sub B/ value decreased with increasing value of A (oxygen parameter). In order to optimize synthesis conditions for the high initial permeability and low /spl eta//sub B/ value, it was best to calcine the sample at 950/spl deg/C and sinter it at 1370/spl deg/C, with A=7.55.     

Effect of sintering temperature on the properties of Cu-Co ferrites prepared by oxalate precipitation method

Polycrystalline Cu-Co ferrite powder was synthesized following oxalate precipitation method. The samples of the compound Cu_0.5Co_0.5Fe₂O₄ were heated at different temperatures in the range of 773-1173 K and were characterized by X-ray diffraction and SEM techniques. The results of XRD show the formation of single-phase cubic spinel structure. The lattice parameter showed a minimum value for the sample heated at 1073 K. It has been observed that grain size increases with the increase in temperature and is maximum (3.2 μm) for the powder sintered at 1173 K.     

MnZn功率铁氧体的研究进展及发展趋势

介绍了宽温超低损耗、高频低损耗和高温高饱和磁感应强度(Bs)MnZn功率铁氧体材料的研究现状,以及添加剂的种类和制备方法的研究,世界上主要软磁铁氧体公司近几年的最新产品情况,指出了MnZn功率铁氧体的发展趋势.从目前的发展状况来看,应用在中低频的功率MnZn铁氧体材料不但要求在较宽的温度范围内具有较低的损耗,同时要求具有高的起始磁导率和饱和磁感应强度.而对于高频功率MnZn铁氧体材料则继续向高频低损耗发展.     

预烧温度对高导磁率MnZn铁氧体微结构和磁性能的影响

研究了预烧温度对高导MnZn铁氧体微结构和主要磁性能的影响,研究表明,由于预烧温度对粉体的活性产生很大影响,所以适宜的预烧温度是良好显微结构和高性能铁氧体的必要保证.适当降低预烧温度可以提高材料的磁导率,而提高预烧温度能够获得较好的频率特性.     

Al替代和烧结温度对NiZn铁氧体磁性能的影响

采用陶瓷工艺制备了Al替代的Ni0.5Zn0.5AlxFe2-xO4(x=0~0.10)铁氧体材料,用XRD、B-H分析仪和阻抗分析仪对其结构和磁性能进行了研究。实验发现,最佳烧结温度为1 250℃,过高和过低的烧结温度不利于降低磁芯损耗。当Al3+替代量x=0.06时,铁氧体能获得较好综合磁性能。     

Effect of sintering conditions on microstructure and magnetic properties of Mn-Zn ferrites

Commercial and specially-prepared Mn-Zn ferrites were characterized, in terms of magnetic performance, microstructure and local composition, by various techniques. The results show the relevance of the structure of the interfaces between grains, the importance of uniform grain size and, finally, the role of composition homogeneity throughout the sample and the atmosphere utilized. The practical relevance of these findings is also discussed.     

Effect of sintering conditions on resistivity and dielectric properties of Ni-Zn ferrites

Resistivity and dielectric properties of the nickel-zinc ferrite composition, Ni0.65Zn0.35Fe2O4, have been studied near different sintering conditions to optimize the sintering schedule for a specific application. Variable sintering parameters in the study include sintering temperature in the range from 1150 to 1300°C and sintering time with 1 h, 2 h and 4 h durations at each sintering temperature. The results indicate that the decrease of resistivity is linear and less rapid upto a sintering schedule of 1250°C/2 h, and thereafter any increase either in sintering temperature or in sintering time causes a rapid decrease of resistivity due to the increased volatilization of zinc from the samples at these temperatures/times. Possible mechanisms contributing to conduction processes in ferrites are discussed in explaining the obtained results. This revised version was published online in November 2006 with corrections to the Cover Date.