Oleg I. Shpotyuk

Controlled thermistor effect in the system CuxNi1–x–yCo2yMn2–yO4

Abstract The problem of selection guidelines for oxide semiconducting ceramics with controlled thermistor effect, prepared on the basis of complex CuxNi1–x–yCo2yMn2–yO4 (0.1⩽x⩽0.8; 0.1⩽y⩽0.9–x) chemical system and restricted by CuMn2O4, MnCo2O4 and NiMn2O4 spinel-structured compounds, is discussed. It is shown that the developed ceramic thermistors with a wide range of predetermined exploitation parameters (rated resistance from 2 to 21,500 Ω, material-specific constant B of NTC thermistor from 2435 to 3365 K), as well as a high level of reliability can be obtained using the proper methods of technological, compositional and design modifications. The attempt to establish a general relationships between chemical composition, technological features of sintering and electrical properties for single-phase ceramics is made, using the method of simplex matrices of the 4-fold D-optimum plan.

Dynamic radiation-induced effects in chalcogenide vitreous compounds

The experimental results on time degradation of radiation-induced darkening effects in vitreous chalcogenide semiconductors of ternary stoichiometric (As 2 S 3 ) y (GeS 2 ) 1 (y 0.1, 0.2, 0.4, 0.6) and non-stoichiometric (As 2 S 3 ) x (Ge 2 S 3 ) 1 (x: 0.1, 0.2, 0.4, 0.8) systems with a variation of the average co-ordination number, Z, are discussed. It is established that adequate model for the quantitative description of these effects can be developed at the basis of bimolecular relaxation function (RF) proper to annihilation of specific structural defects in the form of oppositively charged atoms with various co-ordinations. The observed features of the investigated dynamic radiation-optical changes in these glasses are explained by compositional dependences of their atomic compactness, as well as covalent bond statistics.

Thermal modification of ceramic composites based on manganese-containing cube spinels

The nature of thermostimulated diffusion of silver in ceramic composites based on manganese-containing cube spinels has been studied using the methods of electron-sonde microanalysis, X-ray diffraction, optical and Auger spectrometry.

On the problem of electron-induced anisotropy effect in As2S3-based glasses

Abstract Effect of electron-induced anisotropy was observed in glassy As2S3-based samples irradiated by accelerated electrons (E=2.8 MeV) in the perpendicular plane to the probe light. Spectral and compositional dependences of this effect and its time stability at room temperature were discussed. It was supposed that the microstructural mechanism of the anisotropy effect was connected with electron-induced formation of new oriented (relatively to the electron flow) defects in the form of broken chemical bonds.

The influence of γ-irradiation on electrophysical properties of spinel-based oxide ceramics

Abstract The influence of 60Co γ-irradiation with 1.25 MeV average energy and 1 MGy absorbed dose on electrophysical properties of Cu-, Ni-, Co- and Mn-based spinel ceramic materials in the CuxNi1−x−yCo2yMn2−yO4 (0,1⩽x⩽0,8;0,1⩽y⩽0,9−x) system is investigated. The γ-induced increasing of the electrical resistance is observed for the investigated samples of various compositions. It is supposed that these changes are explained by cationic redistribution in the spinel sublattices of the ceramics.