Alexander A. Andriiko

Specific features of the EPR spectra of KTaO3: Mn nanopowders

The electron paramagnetic resonance spectra of KTaO3: Mn nanocrystalline powders in the temperature range from 77 to 620 K have been measured and studied for the first time. The change observed in the spectra has been investigated as a function of the doping level. The doping regions in which Mn2+ ions are individual paramagnetic impurities have been established, as well as the regions where the dipole-dipole and exchange interactions of these ions begin to occur. The spin-Hamiltonian constants for the spectrum of non-interacting individual Mn2+ ions have been determined as follows: g = 2.0022, D = 0.0170 cm−1, and A = 85 × 10−4 cm−1. A significant decrease in the axial constant D in the KTaO3: Mn nanopowder, as compared to the single crystal, has been explained by the remoteness of the charge compensator from the paramagnetic ion and by the influence of the surface of the nanoparticle. It has been assumed that the Mn2+ ions are located near the surface and do not penetrate deep into the crystallites.

Dielectric Properties and Electron Paramagnetic Resonance of Nanocrystalline Potassium Tantalate

Dielectric constant, losses, and Electron Paramagnetic Resonance (EPR) spectra of the nanocrystalline potassium tantalate were obtained and investigated. In the temperature dependence of the dielectric constant, a wide peak in the interval 20 < T < 40 K was observed. Maximum value of ϵ is 390. This dielectric peak did not shift to higher temperature as the measuring frequency was increased from 25 Hz to 1 MHz. Dielectric losses have several low-temperature frequency-dependant peaks. Obviously, these peaks reflect the reorientation motion of the dipole centers in the material. EPR spectra of nanocrystalline potassium tantalate consist of two types of signals—a ferromagnetic and a paramagnetic signal.

The short form of Mendeleev’s Periodic Table of Chemical Elements: toolbox for learning the basics of inorganic chemistry. A contribution to celebrate 150 years of the Periodic Table in 2019

A condensed overview about the forefathers’ and Mendeleev’s contribution to the compilation of the Periodic Table of Chemical Elements is presented. Milestones en route to the modern Periodic Table are ‘electrification’ of the Periodic Law, discovery of the rare-earth elements and the noble gases, investigation of the atomic structure and discovery of the transuranic elements. Then the contribution focuses on the Table’s short form as toolbox for learning the basics of inorganic chemistry. Similarities and differences in the chemical behavior of elements on the basis of full, close and approximate electronic analogies and the kainosymmetric sublevels (1s, 2p, 3d, 4f) are described. A question/answer section completes the article.