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The investigation focused on nanovoids (free-volume defects) in spinel MgAl2O4 ceramics, synthesized at various temperatures, both before and after saturation (water-immersion), utilizing the positron annihilation spectroscopy method. The findings were analyzed within the framework of a multi-channel model. It was demonstrated that this model integrates channels capturing positrons by volumetric defects and the decay of ortho-positronium atoms. Within this refined approach, the first component reflects the microstructural characteristics of the spinel structure, the second component corresponds to volumetric defects near grain boundaries, while the third pertains to the "pick-off" process of ortho-positronium annihilation within water-filled nanopores of the ceramics. [ABSTRACT FROM AUTHOR]

The electrophysical properties of nanostructured MgAl2O4 ceramics sintered at 1300 °C for 5 h, as well as thick films were obtained and investigated. The study of adsorption-desorption cycles was carried out after sintering and aging test. It is shown that ceramic has a sensitivity to humidity in the range of 25–95% with minimal hysteresis of the characteristic in adsorption-desorption cycles, which can be eliminated after the aging test. Thick films based on it are characterized by hysteresis and loss of sensitivity at low values of relative humidity, which is caused by the clogging of small nanopores. [ABSTRACT FROM AUTHOR]

Surface crystallization processes in the 80GeSe2–20Ga2Se3 glasses thermally annealed at 380 °C for 25 and 80 h were studied by both experimental methods and statistical analysis of images using Python scripts. It is shown that GeSe2 phase is formed as a result of annealing unevenly on glass surface in the form of thread-like crystallites with a length of 1–3 μm. The obtained dependences of number crystallites on their geometric parameters indicate a significant increase in their size (area, length and width) with an increase in the duration of annealing up to 80 h. At the same time, the crystallite growth orientation does not change and is 50°, 90° and 130°. Optimal conditions for crystallization processes can be selected based on the obtained results to prepare stable 80GeSe2–20Ga2Se3 glasses with predetermined optical properties. [ABSTRACT FROM AUTHOR]

Luminescent material with specific properties was engineered by depositing Alq3 thin film on ZnO microdisks covered silicon substrate. The analysis of the polarized photoluminescence (PL) indicated almost twofold increase in polarization degree of the visible PL emission for the obtained samples. The polarization-dependent emission arises due to the anisotropic nature of the molecular alignment. One possible explanation for the observed increase in the degree of polarization is the interaction between the Alq3 thin layer and the ZnO surface, resulting in the alignment of molecules in the Alq3 layer being enhanced. [ABSTRACT FROM AUTHOR]

For the first time, the temperature evolution of the absorption spectra of Alq3 thin film, prepared by the method of vacuum thermal evaporation, was investigated in the range of 16–320 K. The optical energy gaps were obtained from direct allowed transitions at this temperature range by means of Tauc plots. [ABSTRACT FROM AUTHOR]

Low temperature electrical properties of compound materials fabricated by introduction of single- and multi-walled carbon nanotubes with high level of purity into polymer host matrix were studied. Detailed investigation of lateral resistances of the prepared samples in the range of temperatures from 50 to 200 K were performed. Analysis of the conductivity mechanisms in this temperature range was performed by applying Arrhenius equation-based models. Temperature dependencies of lateral resistance were fitted to extract respective activation energies. Distinctions between fabricated specimens reinforced with multi-walled nanotubes and those doped by single-walled carbon nanotubes were demonstrated. It is concluded that composites with multi-walled carbon nanotubes generally exhibit lower resistances as compared to their single-walled counterpart. [ABSTRACT FROM AUTHOR]

Aging processes in the two types of temperature-sensitive Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics (two-phase and with different amount of NiO phase) as well as thick films base on Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics were investigated. It is shown for Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics prepared at 1170 °C with addition treatment at 850 °C that the post-separation process of the second phase continue under heat at temperatures of 125 and 170 °C. It has been found that higher thermal aging leads to more pronounced changes in electrical resistance. Addition temperature influences contribute to the stabilization of ceramic parameters. The aging test at 170 °C results in a 7.5% reduction in electrical resistance, while at 125 °C this value is only 6%. It is shown that NiO phase additives formed during sintering of Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics and located near the grain boundaries of ceramics inhibit the aging process in these materials. This effect is characteristic of fine-grained ceramics obtained by thermal energy converted during sintering. It is established that the kinetics of aging in Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics is described by the relaxation function of DeBast-Gillard or Williams-Watts, regardless of the composition of the ceramics. The aging kinetics in thick films based on Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics at 170 °C is also adequately described by the compression-exponential relaxation function. [ABSTRACT FROM AUTHOR]

Modification of free-volume positron trapping defects in the GaS2–Ga2S3–CsCl chalcogenide glasses was studied using positron annihilation lifetime spectroscopy and Doppler broadening of annihilation radiation methods. It is shown that the addition of CsCl to the main glass matrix leads to agglomeration of internal free-volume defects, which are di- or tri-atomic vacancies. However, an excessive amount of CsCl component causes a decrease in the size and content of these defects in the internal structure of the glass against the background of water adsorption in nanovoids with a radius of 0.3 nm. The obtained results are confirmed by normal and abnormal trends in the correlation of the S parameter, which characterizes the annihilation of positrons with low-momentum valence electrons and the W parameter, which corresponds to the annihilation of positrons with high-momentum core electrons. [ABSTRACT FROM AUTHOR]

Peculiarities of diffusion processes of Ag after aging test at 170 °C in the nanostructured temperature-sensitive Cu0.1Ni0.1Co1.6Mn1.2O4-based thick films are investigated. Microstructural and electrical properties of studied thick films before and after annealing (aging test) are investigated. It is shown that aging of thick films results in diffusion of Ag from contact area in region of grain boundaries. Analytical description of aging processes in these materials was performed using relaxation functions. It is shown, that studied aging kinetics are adequately described by compression–exponential relaxation function. Obtained Cu0.1Ni0.1Co1.6Mn1.2O4-based thick films with stabile electrical properties can be used as temperature-sensitive elements for micro- and nanoelectronics. [ABSTRACT FROM AUTHOR]

The defects/nanopores conversion in the Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics caused by addition phase and monolithization process was studied by positron annihilation lifetime spectroscopy using three-component decomposition of spectra within mixed positron- and positronium-trapping modes. It is established that a larger amount of addition NiO phase in ceramics resulted in void fragmentation with future agglomeration due to monolitization processes. The NiO extracted near intergranular boundaries formed new positron-trapping sites in the Cu0.1Ni0.8Co0.2Mn1.9O4 ceramics. Monolithization of ceramics is accompanied by agglomeration of nanopores with radius centered near 0.3 nm. [ABSTRACT FROM AUTHOR]