Magnetic Hysteresis and Complex Initial Permeability of Cr³⁺Substituted Mn-Zn Ferrites

The impact of Cr3+ ion on the magnetic properties of Mn0.50Zn0.50CrxFe2-xO4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been studied. Ferrite samples were synthesized by combustion method and sintered at various temperatures (1250°C, 1300°C and 1350°C). The structural properties were investigated by means of X-ray diffraction patterns and indicated that the samples possess single phase cubic spinel structure. The lattice parameter decreases with the increase in Cr3+ content, as the ionic radius of Cr3+ ion is smaller than that of Fe3+. The average grain size (D), bulk density (ρB) and initial permeability (μi’ )decreases with increase in Cr3+ content whereas porosity follows its opposite trend. The ρB was found to increase with increase in Cr3+ content as the sintering temperature (Ts) is increased from 1250°C to 1350°C. The Ts affects the densification, grain growth and (μi’ ) of the samples. The (μi’ ) strongly depends on average grain size, density and intragranular porosity. The B-H loops of the compositions were measured at room temperature. The saturation magnetization (Ms), coercivity (Hc) and hysteresis losses were studied as a function of Cr3+ content. The Ms was found to decrease with the increase of Cr3+ content, which is attributed to the dilution of A-B interaction.

ZrO_(2)-Nb_(2)O_(5)复合添加对MnZn铁氧体结构和磁性能的影响

针对开关电源高频小型化需求,采用固相反应制备分子式为(Mn_(0.766)Zn_(0.105)Fe_(0.129))Fe_(2)O_(4)的MnZn铁氧体材料,通过对铁氧体微结构的表征及磁性能的测试,研究了ZrO_(2)和Nb_(2)O_(5)复合添加对MnZn铁氧体显微结构、烧结密度d、初始磁导率μ_(i)、饱和磁通密度B_(s)、剩余磁通密度B_(r)、矫顽力H_(c)以及功耗P_(cv)特性的影响。结果表明,ZrO_(2)和Nb_(2)O_(5)复合添加有利于促进晶粒均匀化和致密化,从而提高了材料烧结密度,能显著降低材料的剩余磁通密度和矫顽力,实现材料的高起始磁导率以及高频低损耗。当ZrO_(2)和Nb_(2)O_(5)复合添加质量比为4∶6时,MnZn铁氧体的μi达到最大值(931),且在高频激励下材料的功率损耗达到最低133 kW/m^(3)(100℃,1000 kHz,50 mT)。

Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites

The ferrites of PC30 （Mn-Zn ferrites） were prepared by using a dry processing route. The effect of Mn-Zn ferrites doped with H3BO3 was investigated on the basis of microstructure analysis. The results of the samples doped with H3BO3 less than 5 × 10^-5 showed that the doping had no significant effect on power loss, initial permeability, fine grain microstructure, and density of Mn-Zn ferrites. With the further increase in H3BO3 doping （up to 1 × 10 ^-4 ）, the microstructure of Mn-Zn ferrites is in the critical state between fine grain and ＂sandwich＂, and the initial permeability and density of Mn-Zn ferrites begin falling quickly; the increased H3BO3 doping also results in deteriorated power loss properties. Thus, the control of the boron content in iron oxide is of utmost importance for the quality of Mn-Zn ferrites in producing process.

添加钛和锡对锰锌铁氧体微结构和高频性能的影响

用氧化物陶瓷工艺制备了MnZn功率铁氧体。结合材料微观结构分析,研究了TiO2,SnO2添加剂对MnZn功率铁氧体起始磁导率μi,电阻率ρ及单位体积高频损耗Pcv的影响。结果表明:为得到优良的高频性能,TiO2和SnO2适宜添加的质量分数(下同)分别是0.2%和0.1%,而复合添加时最佳量分别为0.4%和0.1%。

掺杂对高磁导率低损耗锰锌铁氧体材料磁性能的影响

采用氧化物陶瓷工艺制备了高磁导率低损耗锰锌铁氧体材料,研究了Nb2O5掺杂对材料磁性能的影响。结果表明掺杂0.015%(质量分数)Nb2O5的锰锌铁氧体材料具有较好的磁性能:起始磁导率μi=13386,起始磁导率比温度系数αμ/μi=-0.6×10-6/K,相对损耗因数tanδ/μi=3.2×10-6。

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。

高磁导率MnZn铁氧体TL13材料的研制

介绍了利用氧化物法制备高磁导率（μｉ＝１３５００）ＭｎＺｎ铁氧体ＴＬ１３材料的研制情况。通过对烧结制度如温度、气氛曲线实行精确控制，使铁氧体中保持适当的Ｆｅ２＋含量，同时尽量减少铁氧体中Ｚｎ的挥发，这是获得高磁导率ＭｎＺｎ铁氧体的重要保证。Ｚｎ挥发对铁氧体的显微结构特别是磁芯表层显微结构有较大影响，Ｚｎ的挥发会促进晶粒生长，同时使磁芯表面呈多孔状结构。由于Ｚｎ挥发会随着烧结温度的升高而急剧增大，选择合适的烧结温度非常重要。由于采用了较好的制造工艺方法，ＴＬ１３铁氧体材料具有很好的频率特性，当ｆ＞１００ｋＨｚ时，μｉ才开始下降。

超高B_s系列锰锌铁氧体材料的研制

采用传统陶瓷工艺及通过调整主配方,成功研制出了二峰温度从25℃至140℃的一系列超高饱和磁通密度Mn-Zn铁氧体材料。结果显示,因为锰锌铁氧体材料的饱和磁通密度Bs取决于主配方以及致密度,超富铁主配方是获得超高Bs锰锌铁氧体材料的必要条件;在超富铁主配方中,增加Fe2O3含量或Zn O含量都会使二峰温度升高,与常规配方是完全相反的变化规律;二峰温度越高,最低损耗值越高、高温Bs越高、起始磁导率越低、相对密度越低。