高磁导率Mn—Zn铁氧体材料的试制

本文介绍了磁导率为10000的高μMn—Zn 铁氧体材料试制概况,并扼要说明了高μMn-Zn材料的烧结工艺。     

旋转底式软磁气氛烧结炉的开发与设计

自行研制开发了新一代软磁铁氧体烧结设备--旋转底式气氛烧结炉,它采用旋转底盘、全纤维高温炉衬、分区分组加热、循环强制冷却、计算机全自动控制等技术,具有批次产量大、温度和气氛均匀性好、控制精度高、产品一致性优、操作使用灵活等优越特性.特别适用于高磁导率锰锌铁氧体和低功耗软磁铁氧体等高档铁氧体材料的气氛烧结.     

微波烧结与传统烧结合成的NiCuZn铁氧体组织与性能

采用固相合成法制备了Ni Cu Zn铁氧体材料,对比研究了传统烧结与微波烧结工艺对Ni Cu Zn铁氧体材料的致密化行为、显微结构、磁滞回线和直流偏置特性的影响。结果表明,在微波烧结方式中,材料的致密化曲线向低温方向偏移,烧结致密度得到提高,晶粒尺寸显著增大;对比于传统烧结,微波烧结材料的饱和磁感应强度从312m T提高至479m T,起始磁导率从65提升至170,但在叠加直流偏置电流为3A时,磁导率下降幅度从28.5%增至48.4%。     

烧结温度对镍锌功率铁氧体磁性能的影响

为得到Zn含量不同时NiZn铁氧体材料的最佳烧结温度,用氧化物法制备了NiZn铁氧体材料,研究了烧结温度对材料起始磁导率、功耗、饱和磁感应强度和微结构的影响.结果表明,适宜的烧结温度对制备功耗低、饱和磁感应强度高和较优起始磁导率的NiZn铁氧体材料至关重要,而Zn含量不同时对应材料的最佳烧结温度也各不相同.     

预烧对锰锌铁氧体预烧相及烧结显微结构的影响

采用传统的陶瓷工艺制备了Mn-Zn铁氧体.用X射线衍射(XRD)仪和扫描电子显微镜(SEM)研究了预烧温度对铁氧体预烧相及烧结显微结构的影响.结果表明,在840～1000℃预烧相以(-Fe2O3为主.随着预烧温度的升高,(-Fe2O3的含量逐渐增加,而ZnFe2O4和Mn2O3的含量逐渐减少,Mn3O4固溶于ZnFe2O4形成铁锰锌固溶体,且其含量随着预烧温度的升高呈增大趋势.预烧温度对Mn-Zn铁氧体烧结显微结构和功率损耗有较大的影响.适宜的预烧温度可以获得分布均匀、细小的晶粒及低的功耗,低于或高于此预烧温度,都将造成烧结Mn-Zn铁氧体显微结构的恶化和功率损耗的升高.实验结果表明,对于1340℃的烧结温度,最佳预烧温度为960℃.     

低温烧结BaCoTiFe_(10)O_(19)铁氧体的微结构及高频磁性能

采用传统陶瓷工艺制备了BaCoTiFe10O19铁氧体,结合相结构、显微形貌分析和对材料磁化机理的讨论,主要研究了Bi2O3加入量和烧结温度对钡铁氧体高频磁性的影响.实验表明,起始磁导率和共振频率随Bi2O3加入量的变化存在极值,当Bi2O3的加入量为7.5mol%时钡铁氧体具有较高的磁导率和较低的磁共振频率,偏离7.5mol%均导致磁导率的降低和磁共振频率的升高;高烧结温度导致晶粒尺寸的长大和晶格结构的完善,有利于提高材料的磁导率,同时降低磁共振频率.     

添加LiFe5O8对NiZn铁氧体材料性能的影响

采用传统氧化物法制备NiZn铁氧体材料,考察了添加锂铁氧体LiFe5O8对NiZn铁氧体材料电磁性能的影响。实验表明,添加少量LiFe5O8可以提高NiZn铁氧体材料的烧结密度、起始磁导率和品质因数Q,但是过高的烧结温度会造成材料的晶粒过度生长,从而Q值下降;当LiFe5O8的添加量为5wt%、烧结温度为1060℃时,制备的材料具有较高的起始磁导率和Q值。     

Mn-Zn铁氧体材料磁导率直流叠加特性研究

对Mn-Zn铁氧体磁芯磁导率的直流叠加特性进行了研究.适当调整配方和掺杂对磁芯的直流叠加特性有积极的影响,理论分析了磁导率直流叠加特性与磁芯基本电磁参数(磁滞回线形状和功耗大小)的关系.     

控制氧离子含量的高密度Mn-zn铁氧体的烧结

用MnO、ZnO、Fe_2O_3的混合物,在氧分压适当的气氛中,通过烧结制成了一种Mn-Zn铁氧体,其氧含量等于予定值,密度接近理论值。烧结工艺是根据在不同的温度下Mn-Zn铁氧体生成的机理和致密化过程制定的。为了制成没有气孔的铁氧体,需要在晶粒生长之前,进行致密化。在致密化过程中应使气氛中的氧分压等于Mn-Zn铁氧体所需要的平衡氧分压,以此来控制Mn-Zn铁氧体的氧含量。当频率在20MHz以下时,这种铁氧体的电阻率和频率无关,但是随着Fe含量增加或氧含量的减少而减少。     

高磁导率MnZn的氧本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Ｆｅ＾２＋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,     

Development of Translucent Aluminum Nitride (AIN) Using Microwave Sintering Process

Pure aluminum nitride (AIN) has been successfully sintered to highly translucent form by microwave sintering at 1850°C with a dwelling time of 30–60 minutes. The results showed that the sintering temperature should be at least 1850°C or higher to get reasonable translucency in the AIN sample by the microwave sintering process. On the other hand, the conventional sintering method requires much longer sintering time to obtain a translucent AIN ceramics.     

微波烧结Ni-Zn铁氧体软磁材料的初步研究

采用微波高温烧结炉对Ni-Zn铁氧体软磁材料进行公斤级烧结工艺研究.结果表明,运用微波烧结可以实现Ni-Zn铁氧体材料烧结过程中的快速升温,短时保温,不仅大大降低能源消耗,缩短工艺周期,而且提高了Ni-Zn铁氧体软磁材料物理及机械性能.     

An Investigation Demonstrating the Feasibility of Microwave Sintering of Base-Metal-Electrode Multilayer Capacitors

A microwave sintering technique has been developed for base-metal electrode (BME) multilayer ceramic capacitors (MLCCs). Commercial green chips of size 0603 MLC with nickel electrodes were sintered in a microwave field. With a specially designed susceptor/insulation package to optimize coupling and uniformity of heating, a number of sintering experiments were conducted in the temperature range of 1200 to 1250∘C in a multimode microwave cavity operating at 2.45 GHz under a partially reducing atmosphere. Microstructure of the microwave processed MLCCs was investigated with both SEM and TEM techniques. The dielectric properties of the microwave sintered MLCCs were measured and compared with those sintered using conventional process at 1320∘C and lower pO₂’s ≈ 10^{− 9} atms. The results demonstrate that nickel electrodes remain metallic after microwave sintering even though the pO₂’s were relatively high and would thermodynamically favor NiO. The microwave sintered samples showed a dense, fine and uniform microstructure. The properties of the microwave-sintered samples were comparable to the conventionally sintered samples. The microwave processing was found to have enhanced sintering kinetics of the BME MLCCs, lowering sintering temperature by about 100∘C and also the processing time by about 90%.     

TLM simulation of microwave hybrid sintering of multiple samples in a multimode cavity

Microwave heating technology is a powerful mean to ensure successful sintering of ceramic materials. In sintering experiments, low loss insulators, conductors and high‐loss ceramics are microwaved so as to get optimal mechanical and structural properties. It is known that low‐loss ceramic materials such alumina and zirconia exhibit long waiting time before reaching a critical coupling temperature at which microwaves can be readily absorbed. On the other hand, some ceramics such as silicon carbid have a high loss factor and therefore can be used as a process stimulus for microwave sintering of microwave transparent ceramics. Furthermore, successful sintering experiments often require the use of carefully designed insulating structure in order to minimize thermal gradients caused by heat loss from surfaces. All these problems have led to the introduction of microwave hybrid heating (MHH) schemes using higher dielectric loss susceptors, insulation or coating. Since MHH depend mainly on human expertise, the optimization of sintering experiments will certainly benefit from numerical simulations. The transmission line matrix (TLM) is used to study two MHH schemes where both a susceptor and an insulating matrix were, respectively, used as process stimulus for microwave heating of multiple alumina samples within a three‐dimensional multimode cavity. The effects of such MHH schemes and target settings on electric field distribution and power absorption rates are reported in this paper. Copyright © 2003 John Wiley & Sons, Ltd.     

Phase compositions and microwave dielectric properties of MgTiO<Subscript>3</Subscript>-based ceramics obtained by reaction-sintering method

MgTiO₃-based microwave dielectric ceramics were prepared successfully by reaction sintering method. The X-ray diffraction patterns of the sintered samples revealed a major phase of MgTiO₃-based and CaTiO₃ phases, accompanied with Mg₂TiO₄ or MgTi₂O₅ determined by the sintering temperature and time. The microwave dielectric properties had a strong dependence of sintering condition due to the different phase compositions and the microstructure characteristics. The ceramics sintered at 1360 °C for 4 h exhibited good microwave dielectric properties: a dielectric constant of 20.3, a high quality factor of 48,723 GHz (at 9GHz), and a temperature coefficient of resonant frequency of ?1.8 ppm/^oC. The obtained results demonstrated that the reaction-sintering process is a simple and effective method to prepare the MgTiO₃-based ceramics for microwave applications.     

旋磁铁氧体材料的微波烧结及在环行器中的应用研究

对微波烧结旋磁铁氧体材料进行了初步实验,检测和分析了烧成的材料和由其制成的环行器的主要技术参数,并与传统烧结材料进行了对比.结果表明,微波烧结旋磁铁氧体材料介电损耗较低,用其制作的环行器满足设计要求,损耗减小.该烧结方法具有一定的优越性.     

Electrical properties of conventional and microwave sintered lead free magnetoelectric composites

Abstract

Here we report comparison of dielectric properties of composition synthesized by microwave and conventional sintering. Microwave sintering requires less time and temperature to achieve the same quality of materials as sintered by conventional route. The material sample was prepared by conventional solid state method and sintered in conventional & microwave furnace. Sintered samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. The dielectric and ferroelectric properties were recorded for both the samples and properties were found to improve in microwave sintered samples. There is also a significant improvement in density by microwave processing.     

Dielectric properties of Bi2O3–ZnO–Ta2O5 ceramics sintered by microwave

Here we report dielectric studies carried out on a Bi₂Zn_2/3Ta_4/3O₇ (abbreviated as β-BZT) composition. The material was synthesized by conventional ceramic method and microwave sintering processing. The dielectric properties were studied as a function of frequency and temperature. Dielectric constant of Bi₂Zn_2/3Ta_4/3O₇ ceramics prepared from microwave is slightly smaller than that of the conventional sintered ones. The dissipation factor and temperature coefficient of dielectric constant are low for microwave-sintered samples. Microwave sintering of Bi₂Zn_2/3Ta_4/3O₇ ceramics led to higher densification and the fine microstructure in much shorter time duration compared to conventional procedures, improved microstructure and dielectric properties. To achieve the same densification, it requires 4 h of soaking at the same temperature in conventional sintering process. Microwave sintering method may lead to energy savings because of rapid kinetics of synthesis.     

Microstructure dependence of microwave dielectric characteristics in Ba6-3x Sm8+2x Ti18O54 (x = 2/3) ceramics

Effects of microstructures on the microwave dielectric characteristics of Ba_6-3x Sm_8+2x Ti₁₈O₅₄ (x?=?2/3) ceramics were investigated by controlling the sintering process and the annealing condition. The dielectric constant was sensitive to the porosity in ceramics, but insensitive to the annealing process. Q f value varied with both the annealing atmosphere and the sintering temperature, which indicates the strong reliance of dielectric loss on defects and grain boundaries. τ _f value exhibited a complex dependence on the sintering temperature. The orientation of grains is responsible for the variation of τ _f .