Lossy Titanite-Based Ceramics with Nominal Compositions CaTi1-xMySiO 5 (0 ≦ X, Y ≦ 1, M = Mn, Sn, Zr, Nb) Applicable to Millimeter Electromagnetic Wave Absorber

The titanite-based ceramics with nominal composition CaTi1-xMySiO5 (0≦x≦1, M = Mn, Sn, Zr (y = x), and M = Nb (y = 4x/5)) in which part x of Ti sites are replaced by several kinds of atoms had remarkable increase in both the real and imaginary parts of complex relative permittivity around x = 0.0125~0.1 compared with those of pure titanite CaTiSiO5 ( x = 0) at 70 GHz. Real part varied from 3 to 43, and the imaginary part from 0 to 12 (tangent delta from 0 to 0.28). No reflection condition is fulfilled for M = Zr when x = 0.05, d/λ0 =0.042, and for M = Nb in both cases when 0 < x < 0.0125, d/λ0 = 0.05 and 0.1 <x < 0.2, d/λ0 =0.042, where d is thickness of the plate sample and λ0 is the wavelength of incident electromagnetic wave. The dominant dielectric dispersion may occur due to difference of ionic polarization between Ti4+ ions and Mn4+, Sn4+, Zr4+, or Nb5+ ions relative to O2- ions, which becomes inactive and saturates around x = 0.0125~0.05. From the measurement of the lattice parameters, a, b, c, and the angle β, characterizing monoclinic crystal structure, this saturation may have close correlation with some structural rearrangement of constituting atoms, Ti and substituted M atoms in CaTi1-xMySiO5

High permittivity dielectrics

This chapter discusses high permittivity dielectrics such as hafnium oxide and zirconium oxide and how the phonons of such materials, their band and polarization behavior and silicon interact. High permittivity materials are used as dielectrics with semiconductors. A prominent use for these materials is in suppressing tunneling while enhancing the field effect. High permittivity arises strongly from ionic polarization. So, the low frequency response for high permittivity materials is very different from that of silicon dioxide. Transition metal oxides’ high permittivity comes together with soft phonons. With phonons soft, that is of low phonon energy, the interactions and transport behavior of semiconductors can change significantly through a modified Fröhlich interaction, because of the presence of high permittivity materials nearby. These various issues are analyzed.

Promoting Effect of H+ and Other Factors on NO Removal by Using Acidic NaClO2 Solution

In this study, NaClO2 was selected as a denitration oxidant. In order to clarify the mechanism of NaClO2 as an oxidation agent for NO removal efficiency, the effects of H+ and other factors (NaClO2 concentration, temperature, and the other gas) on the NO removal efficiency were investigated. NaClO2 showed a promotional ability on NO removal, whose efficiency increased with the increase of NaClO2 concentration. One hundred percent removal efficiency of NO could be achieved when the NaClO2 concentration was 0.014 mol/L. Furthermore, raising the reaction temperature benefited the removal of NO. The lower the pH, the better the NO removal efficiency. The promoting effect of H+ on the NO removal was studied by the Nernst equation, ionic polarization, and the generation of ClO2. Under the optimal conditions, the best removal efficiency of NO was 100%. Based on the experimental results, the reaction mechanism was finally speculated.