Ni-Zn ferrites

Spray drying of aqueous suspensions Example. (Ni, Zn, Fe) sulphates (in air) — Ni, Zn ferrite. 

Figure 7-4 Damping Out the High AV/At Wiggle by Inserting a Small Lossy Ni-Zn Ferrite Bead... 

Most spinel ferrites used in device applications are not simple ternary oxides but rather contain proprietary mixtures of several different magnetic ions tailor made for specific applications. So-called (Mn, Zn) ferrites of general formula Zn+ c Fe+ i-x[Mn+ i cF ]04 and related (Ni, Zn) ferrites... 

Typical fillers glass fiber, carbon fiber, graphite, metal powders (bronze), molybdenum sulfide, boron nitride, carbon black, Ni-Zn ferrite... 

With these improvements, we could do away with the heatsinks altogether. The transistors would now run cool-to-the-touch, even while free-standing. No thermal trip was required. The transistors could also now be the cheaper and higher gain MJE13005. As for the input surge test, we replaced the filter with a smaller differential mode toroidal filter deliberately made of lossier Ni-Zn ferrite material, and simultaneously increased the input bulk... 

A classical, extensively studied example is the so-called Ni-Zn ferrites, with the general formula ... 

Aburto, S., Jim6nez, M., Marquina, M. L. Valenzuela, R. (1982). The molecular field approximation in Ni-Zn ferrites. In Ferrites Proceedings of the Third International Conference. Eds H. Watanabe, S. lida and M. Sugimoto. Center for Academic Publications, Tokyo, pp. 188-91. 

Using a similar technique, Chen et al. (1988) have produced ultrafine particles of Ni-Zn ferrites in the 3-30 nm range. A solution of the nitrates of Ni, Fe and Zn was precipitated by addition of N2H4 and KOH. The... 

Ni-Zn ferrites have been obtained by freeze-drying a high density with... 

Chen, C. J., Bridger, K., Winzer, S. R. PaiVerneker, V. (1988). A novel low-temperature preparation of Ni-Zn ferrite and the properties of the ultrafine particles formed. Journal of Applied Physics, 63, 3786-8. 

Itoh, H., Takeda, T. Naka, S. (1986). Preparation of nickel and Ni-Zn ferrite films by thermal decomposition of metal acetylacetonates. Journal of Materials Science, 21, 3677-80. 

Tseng, T. Y. Lin, J. C. (1989). Preparation of fine grained Ni-Zn ferrites. Journal of Materials Science Letters, 8, 261-2. 

Anisotropy constants vary considerably with temperature. In most cases, anisotropy decreases steeply from a high value at low temperature and then slowly decreases down to zero at 7. The temperature dependence of the anisotropy constant for Zn,jNii Fe204 ferrites is shown in Fig. 4.27, for various compositions. At low temperatures, total anisotropy can be described in terms of anisotropy contributions from each cation (Kanamori, 1963). The anisotropy of Ni-Zn ferrites at 4 K, for example, can be obtained from contributions of Fe in octahedral and tetrahedral sites (Broese van Groenou, Schulkes Annis, 1967). The contribution from some cations, in particular Co and Fe, is positive above a given concentration of any of these cations, the anisotropy constant at low... 

Fig. 4.27. Temperature dependence of the magnetocrystalline anisotropy constant in the Ni-Zn ferrite system for various compositions. (Adapted from Broese van Groenou, Schulkes Artrtis, 1967.)...

The thermal behaviour of the initial permeability is important for many applications. In a representative spinel solid solution series, Ni-Zn ferrites, the relative permeability can be varied from 20 for NiFe204, to 8000 for Zno.7Nio.3Fe204, Fig. 4.47. As stated by Eq. (4.59), the initial permeability varies as Since anisotropy decreases faster than... 

Fig. 4.6S. Effect of Fe content, d, on the electrical conductivity of Ni-Zn ferrites. (Adapted from Van Uitert, 1956.)...

Globus, A. Valenzuela, R. (1975). Influence of deviations from stoichiometry on the magnetic properties of Zn-rich Ni-Zn ferrites. IEEE Transactions on Magnetics, MAG-11, 1300-2. 

Ni-Zn ferrites are remarkable scientifically and technologically because of their high electrical resistivity, magnetic properties and several technological... 

Table 15.1 Relative magnetic permeability values of some Ni-Zn ferrites at 25 °C.

In the context of magnetic ceramics, Ni-Zn ferrite awakens much interest of scientific community for its high permeability and high resistivity. This fact constitutes a reason for the application of this material in microwave devices. This absorption capacity may be generated or potentiated by changing material magnetic and dielectric properties. 

Table 15.1 lists the magnetic permittivity values of some Ni-Zn ferrites in room temperature. It is worth mentioning that variations in these values due to differences in morphological parameters, processing and structure are expected. 

Boon, M.S., Serena Saw, W.P., Mariatti, M. Magnetic, dielectric and thermal stability of Ni-Zn ferrite-epoxy composite thin films for electronic applications. J. Magn. Magn. Mater. 324, 755-760 (2012)... 

K. Kondo, T, Chiba, H. Ono, and S. Yoshida, Y. Shimada, N. Matsushita, M. Abe, High-frequency transport properties of spin-spray plated Ni-Zn ferrite thin films, J. Appl. Phys.,... 

Spray drying of solutions has been found to be useful for the preparation of ferrite powders (88). For Ni-Zn ferrite, the solution of sulfates was broken up into droplets (10-20 p.m) by a rotary atomizer. The powder obtained by spray drying was in the form of hollow spheres having the same size as the original droplets. Calcination at 800-1000°C produced a fully reacted powder consisting of agglomerates with a primary particle size of 0.2 xm. The ground powder (particle size < 1 p,m) was compacted and sintered to almost theoretical density. 

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