In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

A review on MnZn ferrites: Synthesis, characterization and applications.

A comprehensive overview of the up-to-date research activities targeting electromagnetic interference (EMI) shielding is provided, focusing on the multifunctional polymer nanocomposites (PNCs) reinforced with a variety of conductive fillers. The unique dielectric, magnetic and other physicochemical properties derived from certain morphology-, composition-, and loading-controlled nanostructures for EMI shielding behaviors are elaborated. The conductive fillers including three different categories: carbon, metals, and conductive polymers in the EMI shielding PNCs are discussed together with their synergistic effects on enhancing the EMI shielding property. The enhanced electromagnetic interference shielding effectiveness and mechanisms are discussed with detailed examples and are envisioned to provide rational design of next generation lightweight EMI shielding materials.

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An Overview of Electrically Conductive Polymer Nanocomposites toward Electromagnetic Interference Shielding

Nickel Spinel Ferrites: A review

Effects of sintering temperature and Bi2O3 content on microstructure and magnetic properties of LiZn ferrites

Effects of Bi2O3 on FMR linewidth and microwave dielectric properties of LiZnMn ferrite

The grain growth, densification and magnetic properties of Bi2O3 doped NiZn ferrites prepared by a solid-state reaction method were investigated. Addition of a moderate content of Bi2O3 additive, to NiZn ferrite, due to its liquid phase sintering enhanced the diffraction intensity while excessive content of Bi2O3 produced a thick liquid phase layer at the grain boundaries and retarded mass transfer during sintering. Thus the x-ray diffraction peaks exhibited reduced intensity. In samples with higher additive content, Bi2O3 segregated at the grain boundaries as a liquid phase layer. This phenomenon could be confirmed by backscattering electron image. The grain growth of Bi2O3 doped NiZn ferrites was discussed by using the liquid phase sintering mechanism. Bi2O3 promoted grain growth via liquid phase sintering, and the addition of the optimum content of Bi2O3 could enhance the density of the sample and reduce its porosity. The NiZn ferrite samples containing x = 0.20, 0.08 and 0.04 sintered at 1180 °C, 1220 °C and 1250 °C, respectively, exhibited high permeability (μi) and low core losses (PL) at 50 kHz and 150 mT. The losses here were composed mainly of hysteresis loss, both eddy current loss and residual loss were ignored. The addition of proper content of Bi2O3 can improve the saturation induction (Bs) and reduce the coercivity (Hc) by liquid phase sintering.

http://iopscience.iop.org/article/10.1088/0022-3727/41/23/235002/pdf

Grain growth, densification and magnetic properties of NiZn ferrites with Bi2O3 additive

As the macro behavior of the strength of exchange interaction, state of the art of Curie temperature Tc, which is directly proportional to the exchange integrals, makes sense to the high-frequency and high-reliability microwave devices Challenge remains as finding a quantitative way to reveal the relationship between the Curie temperature and the exchange integrals for doped barium hexaferrites Here in this report, for La-substituted barium hexaferrites, the electronic structure has been determined by the density functional theory (DFT) and generalized gradient approximation (GGA) By means of the comparison between the ground and relative state, thirteen exchange integrals have been calculated as a function of the effective value Ueff Furthermore, based on the Heisenberg model, the molecular field approximation (MFA) and random phase approximation (RPA), which provide an upper and lower bound of the Curie temperature Tc, have been adopted to deduce the Curie temperature Tc In addition, the Curie temperature Tc derived from the MFA are coincided well with the experimental data Finally, the strength of superexchange interaction mainly depends on 2b-4f1, 4f2-12k, 2a-4f1, and 4f1-12k interactions

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Zhong Yu

Papers

Effects of sintering temperature and Bi2O3 content on microstructure and magnetic properties of LiZn ferrites

Effects of Bi2O3 on FMR linewidth and microwave dielectric properties of LiZnMn ferrite

Grain growth, densification and magnetic properties of NiZn ferrites with Bi2O3 additive

Calculation of exchange integrals and Curie temperature for La-substituted barium hexaferrites

Rietveld refinement, microstructure and ferromagnetic resonance linewidth of iron-deficiency NiCuZn ferrites