Magnetic ceramics properties, measurement

In summary, the picture of these superconducting ceramics at this time is one which shows an extremely complex relationship between the various properties and the processing conditions. It is clear that almost every property measured, i.e. magnetic,... 

In this book, an attempt is made to provide an overview of the science of magnetic ceramics. Chemical aspects are covered in terms of synthetic methods and crystallography. Physics is introduced to provide a theoretical basis to magnetism, which is necessary to interpret the property measurements. Materials science links together physics and chemistry and, in addition, provides the framework for a scientific understanding of fabrication and testing, leading to applications. 

The above consideration of nanoparticles has been carried out in a supposition that they have more or less the same size. To be more precise, we assumed that the width of the nanoparticles sizes distribution function is smaller then its mean value. The mean value R is usually extracted from, e.g., X-Ray diffraction measurements [91] and it is supposed, that the size of all the particles corresponds to R. In this part we will show, that the neglection of sizes distribution can lead to incorrect results, when measurements are performed on the samples with essential scattering of sizes. Besides that, actually the size distribution defines the spectral lines inhomogeneous broadening. Moreover, it essentially influences the observed anomalies of many physical properties (like specific heat and dielectric or magnetic permittivity) of nanomaterials. Note that in real nanomaterials, like nanoparticles powders and/or nanogranular ceramics there is unavoidable size distribution which in general case should be taken into account. However, we will show below, that in perfect samples, where the width of size distribution is small, it is possible to suppose safely that all particles have the same size. In this part we primarily follow the approaches from the paper [92]. 

According to the matrix, nanocomposites may be classified into three categories i) Ceramic matrix nanocomposite, ii) metal matrix nanocomposites, and iii) polymer matrix nanocomposite. In the first group of composites the matrix is a ceramic material, i.e., a chemical compoxmd from the group of oxides, nitrides, borides, silicides, etc. In most cases of ceramic-matrix nanocomposites the dispersed phase is a metal, and ideally both components, the metallic one and the ceramic one, are finely dispersed in each other in order to elicit the particular nanoscopic properties. Nanocomposites from these combinations were demonstrated to improve their optical, electrical and magnetic properties [5,4], as well as tribological, corrosion-resistance and other protective properties [6,5]. Thus the safest measure is to carefully choose immiscible metal and... 

Chapter 200, by Peter M. Allenspach and M. Brian Maple, reviews some aspects of the low-temperature heat capacity of the ceramic oxide superconductors. These measurements yield valuable information about the electronic, lattice, magnetic, crystalline electric field and hyperfine nature of the various rare-earth cuprate materials, and in that respect compliment other physical property studies, such as neutron diffraction, inelastic neutron scattering, and various spectroscopic measurements. The authors review the heat-capacity properties of the stoichiometric RBaCu307 compoimds and oxygen-deficient materials, and show that there are significant differences. The heat capacities of other lanthanide cuprates, such as RBa2Cu40g and R2B4CU7O14+X, are also discussed. 

The magnetization behavior B versus H) of ferrite ceramics may be measured by an induction method. Other properties frequently measured are initial permeability,... 

The history of ceramics is as old as civilization, and our use of ceramics is a measure of the technological progress of a civilization. Ceramics have important effects on human history and human civilization. Earlier transitional ceramics, several thousand years ago, were made by clay minerals such as kaolinite. Modem ceramics are classified as advanced and fine ceramics. Both include three distinct material categories oxides such as alumina and zirconia, nonoxides such as carbide, boride, nitride, and silicide, as well as composite materials such as particulate reinforced and fiber reinforced combinations of oxides and nonoxides. These advanced ceramics, made by modem chemical compounds, can be used in the fields of mechanics, metallurgy, chemistry, medicine, optical, thermal, magnetic, electrical and electronics industries, because of the suitable chemical and physical properties. In particular, photoelectron and microelectronics devices, which are the basis of the modern information era, are fabricated by diferent kinds of optical and electronic ceramics. In other words, optical and electronic ceramics are the base materials of the modern information era. 

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