Multi-step sintering processing of ferrites having enhanced magnetic properties
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.39
Multi-step sintering processing of ferrites having enhanced magnetic properties Jia, Ning1; Zhang, Huaiwu1; and, Harris, Vincent G.2
1
University of Electronic Science and Technology of China, Chengdu, Sichuan, China.
2
Center for Microwave Magnetic Materials and Integrated Circuits, Northeastern University, Boston, MA
02115 USA
Abstract
Traditional synthesis of high-performance bulk ferrites include complex sintering procedures where temperature and soak times to obtain high densities and excellent magnetic properties. Most ferrites must be sintered at hundreds degree centigrade approaching or surpassing 1000oC, and for YIG (yttrium iron garnet), the sintering temperature should be approximately 1450℃. The high sintering temperatures limit the applications of ferrites, for example, the low temperature co-sintering of ceramics with silver electrodes and/or ground planes. For decades, researchers have explored the use of ion-doping, sintering aids, and microstructural refinement. Here, we study the optimization of the sintering profile including multiples temperature and soak times for doped Bi-YIG simples. The results show an improvement in soft magnetic and gyromagnetic properties attributed to the homogenization of grain size and morphology.
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Introduction Ferrites have been widely studied for decades since their introduction in modern high frequency devices during the early 1950s. A wide variety of ferrite materials are used in many applications for the transmission, reception, and manipulation of microwave electromagnetic signals across high frequency to quasi-optical bands [1, 2]. With the continuous development of modern communication technologies, the miniaturization and integration of ferrites has become of paramount importance. Low temperature co-fired ceramics (i.e., LTCC) have become an attractive method for the industrial scale processing of ferrites meeting needs for compact, lightweight, and highperformance and advanced functional for many commercial electronic devices [3]. However, in LTCC metals interconnects, consisting of Cu, Ag, and Au, have comparatively low melting temperatures than most ferrite. With the goal of combining these two disparate materials – Ag and ferrite, the ferrite must maintain superior magnetic properties upon sintering at < 960 ⁰C –below the melting temperature of Ag [46]. Yttrium iron garnet (YIG, Y3Fe5O12) is a ferrite that has a cubic structure of space group Ia3d. It has unmatched high-frequency magnetic properties, as well as low magnetic loss and intrinsically low magnetic spin-wave damping, leading to very narrow ferromagnetic resonance (FMR) linewidths [7-9]. This ferrite has been widely studied and applied in circulators, isolators and filters [10-12].
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