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

Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics

This is the first time we report that simply air plasma treatment can also enhances the optical absorbance and absorption region of titanium oxide (TiO2) films, while keeping them transparent. TiO2 thin films having moderate doping of Fe and Co exhibit significant enhancement in the aforementioned optical properties upon air plasma treatment. The moderate doping could facilitate the formation of charge trap centers or avoid the formation of charge recombination centers. Variation in surface species viz. Ti3+, Ti4+, O2−, oxygen vacancies, OH group and optical properties was studied using X-ray photon spectroscopy (XPS) and UV-Vis spectroscopy. The air plasma treatment caused enhanced optical absorbance and optical absorption region as revealed by the formation of Ti3+ and oxygen vacancies in the band gap of TiO2 films. The samples were treated in plasma with varying treatment time from 0 to 60 seconds. With the increasing treatment time, Ti3+ and oxygen vacancies increased in the Fe and Co doped TiO2 films leading to increased absorbance; however, the increase in optical absorption region/red shift (from 3.22 to 3.00 eV) was observed in Fe doped TiO2 films, on the contrary Co doped TiO2 films exhibited blue shift (from 3.36 to 3.62 eV) due to Burstein Moss shift.

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Formation of oxygen vacancies and Ti 3+ state in TiO 2 thin film and enhanced optical properties by air plasma treatment

Semiconductor photocatalysts have received much attention in recent years due to their great potentials for the development of renewable energy technologies, as well as for environmental protection and remediation. The effective harvesting of solar energy and suppression of charge carrier recombination are two key aspects in photocatalysis. The formation of heterostructured photocatalysts is a promising strategy to improve photocatalytic activity, which is superior to that of their single component photocatalysts. This Feature Article concisely summarizes and highlights the state-of-the-art progress of semiconductor/semiconductor heterostructured photocatalysts with diverse models, including type-I and type-II heterojunctions, Z-scheme system, p–n heterojunctions, and homojunction band alignments, which were explored for effective improvement of photocatalytic activity through increase of the visible-light absorption, promotion of separation, and transportation of the photoinduced charge carries, and enhancement of the photocatalytic stability.

State‐of‐the‐Art Progress in Diverse Heterostructured Photocatalysts toward Promoting Photocatalytic Performance

This review aims to summarise the progress in some materials and structures for electromagnetic applications, such as microwave absorption, electric shielding and antenna designs, which have been developed in recent years. Composites with spherical powders for microwave absorption focus mainly on those based on ferrites (especially hexagonal), carbonyl iron and related alloys and various newly emerged nanosized materials. Composites with long conductive fibres as fillers will be summarised, with speical attentions to prediction, measurment and evaluation of their performances. Metamaterials include structures for microwave absorbing applications, tunable materials or structures with reflection or transmission coefficients that are tunable by external magnetic or electric fields, and specially designed structures for microwave absorbing applications, with thickness much smaller than that of conventional composite materials and performances that can be optimised by the physical properties of substra...

Recent progress in some composite materials and structures for specific electromagnetic applications

The magnetic and dielectric properties of microwave sintered yttrium iron garnet (YIG)

Enhanced ferromagnetic properties of low temperature sintering LiZnTi ferrites with Li2O–B2O3–SiO2–CaO–Al2O3 glass addition

Li2O-B2O3-SiO2-CaO-Al2O3 and Bi2O3 co-doped gyromagnetic Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite ceramics for LTCC Technology

In the present work, the Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite, a low temperature sintered gyromagnetic material, was prepared via solid-state reaction method. A pure spinel phase can be formed with a sintering temperature ranging from 880°C to 920°C, which allows them to be co-fired with silver. The addition of ZnO–Bi2O3–SiO2 (ZBS) glass in the Li0.43Zn0.27Ti0.13Fe2.17O4 ferrites contributes significantly to the grain growth and ferromagnetic properties through a low temperature (~900°C) sintering process. Results show that the addition of ZBS glass (0.125–2.00 wt%) cannot only double saturation induction (from ~150 to 300 mT) but also drastically reduce ferromagnetic resonance line width at 9.3 GHz (from 920 to 228 Oe), indicating that ZBS glass is a good candidate for lowing the sintering temperature of LiZnTi ferrites.

Low Temperature Firing of Li0.43Zn0.27Ti0.13Fe2.17O4 Ferrites with Enhanced Magnetic Properties

The fabrication and photocatalytic properties of visible-light driven CuInSe2/TiO2 heterojunction films are reported. CuInSe2 nanoparticles (NCs) were synthesized using a solvothermal method and then decorated onto self-organized anodic TiO2 nanotube (NT) arrays through an electrophoretic deposition process, forming a CuInSe2 NC/TiO2 NT hetero-structure film. An increase in deposition time produced an increased amount of CuInSe2 NCs loaded onto the TiO2 NT arrays, expanding the light-absorption range of the CuInSe2 NCs/TiO2 NTs film from 400 nm to 700 nm. Photocatalytic degradation results show that activities of the CuInSe2 NCs/TiO2 NTs films were significantly enhanced compared to that of pure TiO2 NTs (degradation rate constant k increased from 3 × 10-3 min-1 to >1 × 10-2 min-1). Particularly, the CuInSe2 NCs/TiO2 NTs with 50 min electrophoretic deposition show the highest degradation rate, k = 1.6 × 10-2 min-1 (more than 5 times greater than that of the pure TiO2 NTs film), due to optimization of CuIn...

Lijun Jia

Papers

The magnetic and dielectric properties of microwave sintered yttrium iron garnet (YIG)

Enhanced ferromagnetic properties of low temperature sintering LiZnTi ferrites with Li2O–B2O3–SiO2–CaO–Al2O3 glass addition

Li2O-B2O3-SiO2-CaO-Al2O3 and Bi2O3 co-doped gyromagnetic Li0.43Zn0.27Ti0.13Fe2.17O4 ferrite ceramics for LTCC Technology

Low Temperature Firing of Li0.43Zn0.27Ti0.13Fe2.17O4 Ferrites with Enhanced Magnetic Properties

Enhanced visible-photocatalytic activity of anodic TiO2 nanotubes film via decoration with CuInSe2 nanocrystals.