Registration Number
0223U004990,
(0121U109484)
, R & D reports
Title
New superionic argyrodite based conductors for highly effective solid-state energy sources
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Нові суперіонні провідники на основі аргіродитів для високоефективних твердоелектролітичних джерел енергії
Head
Kokhan Oleksandr P., к.х.н.
Registration Date
12-12-2023
Organization
Uzhhorod National University State Higher Educational Institution
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The development of technology of obtaining optimal Ag+-conductive materials, which are based on argyrodite structure compounds Ag7GeS5I and Ag7SiS5I, suitable for the use as solid-state energy sources, is the scope of the present project. Moreover, the aim of the work consists of next points: optimization of processes of investigated materials obtaining; investigation of structural, electrical, acoustic, mechanical, and optical properties; study of the influence of different types of disorders on the structural and physical parameters, as well as order-disorder processes at cationic substitution and transition from three-dimensional bulk to nanoscale structures; development of physical and technical bases for the creation of new solid-electrolytic energy sources.
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Based on the data of differential thermal analysis (DTA) and X-ray diffraction analysis (XRD), close to optimal technological regimes for the synthesis and growth of single crystals of solid solutions of Ag7(Ge1-xSix)S5I composition (where x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were developed . The methodology for the preparation of superionic ceramics based on micro- and nanocrystalline powders of Ag7(Ge1-xSix)S5I solid solutions has been improved. The obtained single crystalline and ceramic (obtained from micro- and nanocrystalline powders) materials were studied using X-ray diffraction and microstructural (scanning electron microscopy and energy dispersive X-ray spectroscopy) analyses, optical methods (diffuse reflection, optical transmission, spectral ellipsometry), electrical conductivity (impedance spectroscopy) and microhardness measurements. The mechanism of the Ag7(Ge1-xSix)S5I solid solutions formation has been established for the first time. Using the density functional theory, it was found that the cationic substitution Si+4→Ge+4 leads to an increase in the stability of the crystal lattice. Studies of microhardness changes within the framework of the gradient theory of plasticity indicate plastic deformation of single crystals and ceramic samples of Ag7(Ge1-xSix)S5I solid solutions. According to the results of electrical conductivity measurements by impedance spectroscopy, single-crystal and ceramic samples of Ag7(Ge1-xSix)S5I solid solutions are characterized by a rather low value of the electronic and high values of the ionic components (σion>>σel) of conductivity. It has been shown that reducing the size of crystallites (applicable to ceramic materials) leads to an increase in the ionic component of conductivity, which makes it possible to increase the overall manufacturability of materials for practical applications. Using optical methods, the presence of a compositional disorder of the crystal structure at cationic Si+4→Ge+4 substitution was established.
Product Description
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Bilanych Vitaliy Stepanovych
Malakhovskaya Tetiana O.
Pohodin Artem I.
Pop Mykhailo M.
Shender Iryna O.
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2023-12-12
