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The process of phase formation of new antimony pyrochlore (sp. gr. Fd-3m) Bi2.7Zn0.46Ni0.70Sb2O10 + ? during solid-phase synthesis from oxide precursors was studied. The process of solid-phase synthesis of antimony pyrochlore Bi2.7Zn0.46Ni0.70Sb2O10 + ? is a complex multi-stage process. It was shown that the interaction of oxide precursors occurs at a temperature of 600 ?С and higher, bismuth stibatate – Bi3SbO7 is formed as an impurity phase. Oxide precursors, including bismuth (III) and antimony (III, V) oxides, are fixed in the sample up to 750 ?С, at which the intermediate cubic phase Bi3M2/3Sb7/3O11 (sp. gr. Pn-3) is formed, stable up to 900 ?С. The pyrochlore phase in the sample appears at 650 ?С, a significant increase in the proportion of pyrochlore occurs at a temperature of 850 ?С and above. Phase-pure pyrochlore is formed at 950…1050 ?С. At a temperature of 1050 ?С, sintering of fine-grained ceramics occurs, a low-porosity microstructure is formed due to the fusion of small grains with the formation of coarse crystallites with a longitudinal size of 2…4 ?m. The unit cell parameter of pyrochlore in the range of 650…1050 ?С changes non-monotonically, at 800 ?С the minimum value of 10.464 ? is fixed, the unit cell constant of phase-pure pyrochlore Bi2.7Zn0.46Ni0.70Sb2O10 + ? is equal to 10.474 ?.
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The technological properties of clay raw materials from the Stolinskiye Khutora deposit (Vidibor area, Brest region) were studied, which allowed it to classify according to GOST 9169–2021. It was found that the clay is refractory, highly plastic, semi-acidic or acidic (depending on the depth), with a high or medium content of coloring oxides, coarsely dispersed, unsinterable in the firing temperature range of 900…1200 ?. The phase composition of the clay material, as well as the processes occurring upon heating were investigated. It was deter-mined that this clay can be used for producing ceramic bricks, clinker material, as well as ceramic floor tiles. Samles of building ceramics synthesized in the laboratory using clay from the Stolinskie Khutora deposit had the necessary set of physicochemical and performance characteristics.
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The results of a study of the chemical and mineralogical composition of the mineral hematite from the Kyzyltash deposit before and after firing are presented, and methods for its enrichment are selected. Red and brown pigments were synthesized and the results of X-ray diffraction and electron microscopy analyzes were analyzed. The coloring properties of the resulting red and brown pigments were studied. It has been established that hematite from the Kyzyltash deposit can be used as a raw material component at production enterprises in the building materials industry of Uzbekistan for the preparation of ceramic glazes and coloring pigments.
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Spectral-luminescence properties of zinc-phosphate ZnO–P2O5 (PZ) glasses doped with 0.25…1.00 mol. % Er2O3 were studied. It has been shown that an increase in the Er2O3 concentration in the synthesized glasses leads to intensity growth of the luminescence band with a maximum at a ~1537 nm. The values of the intensity phenomenological parameters ?t (t = 2, 4, 6) of Judd–Ofelt were estimated and the probabilities of radiation transitions, branching ratio, cross sections of the induced radiation and radiation lifetimes of the excited state were calculated. The obtained results demonstrate the potential of using the material under study as an infrared amplifier.
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The article presents the results of a study of the dielectric properties and harmonic coefficient of lead zirconate-based ceramics synthesized at different sintering temperatures from the initial PbO and ZrO? powders with particle sizes of 500 and 20 nm, respectively. It has been established that the use of nanodispersed powders makes it possible to reduce the sintering temperature compared to traditional technical ceramics made from 1 ?m particles. The maximum value of the dielectric constant was recorded for ceramics sintered at a temperature of 1100 °C. With an increase in the sintering temperature above 1200 °C, a decrease in the dielectric constant is observed, however, upon cooling in the range of 226…208 °C, a ferroelectric phase is formed.
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Ceramics based on beta-CaSiO3 wollastonite with additives of perovskite and sintering aluminum-copper-lithium additive were obtained. The effect of a sintering additive on ceramic and dielectric properties in the CaCiO3/Al2O3–CuO–Li2CO3 and CaCiO3/CaCiO3–Al2O3–CuO–Li2CO3 systems is described. The thermal conductivity ? of the obtained samples is in the range of 0.43...0.65 W/(m?K), which is typical for wollastonite ceramics. The dielectric constant was ?r = 4.9...8.0, the tangent of the dielectric loss angle – tg? = (15.3...17.9)·10–3 at a frequency of f = 1 MHz, and the average density is ?ср = 2.44...2.63 g/cm3. Sintering of the samples was carried out at temperatures of 875...950 ?С. The properties of the resulting ceramics, combined with low thermal conductivity, meet the requirements for heat-resistant ceramic cases and plates for microelectronics applications using LTCC technology.
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The results of the study of the effect of different fractional fractions of the stabilizing impurity of yttrium oxide Y2O3 on the microstructure, phase composition, and mechanical properties of ceramics based on zirconium dioxide ZrO2, obtained by electron-beam sintering in the forevacuum pressure region, are presented. Ceramics with a mass content of Y2O3 ranging from 1.8 to 31.5 % were studied. It has been shown that increasing the proportion of Y2O3 in ZrO2-based ceramics leads to a decrease in the density of the sintered ceramics, but it also contributes to the stabilization of the tetragonal phase of ZrO2. This has a positive effect on its strength characteristics, taking into account the absence of pressure during the sintering process. It has been established that the optimal content of Y2O3 for achieving high microhardness (up to 5.64 GPa) is 15 %.
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The physico-mechanical properties of corundum ceramics based on domestic alumina grade Г-00 have been studied. It was found that the best mechanical strength indicators were obtained for ceramics fired at a temperature of 1400 °C, containing 5 wt. % of yttrium oxide and 5 wt. % of the eutectic additive MnO–TiO2. The prospects of import substitution of alumina are shown.
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Materials based on silicon carbide (SiC) and the SiC–20B4C–1C–0.5B system were produced using spark plasma sintering. The properties of powder mixtures and finished products were studied using thermal analysis, electron microscopy, X-ray diffraction analysis, and flexural testing. Thermal analysis showed that SiC powders with B and C additives had an accelerated mass loss, indicating their ability to sinter more effectively and form a grain boundary phase consisting of boron-carbon compounds. The addition of boron carbide led to the formation of an additional hardening phase in SiC. The main phase in the material was 6H-SiC polytype with a hexagonal alpha-SiC structure. Mechanical testing of the SiC-20B4C-1C-0.5B composite material revealed that its bending strength at RT reached 332 MPa. The study was not completed.
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The possibility of using pyrolysis products of oil-containing waste, including oil sludge, in the synthesis of porous ceramics is shown. High carbon content in pyrolysis products of oil sludge determines the expediency of their application as a burnout component for partial replacement of raw material in the production of aluminosilicate ceramics. The presence of metal oxides of natural and anthropogenic origin in pyrolysis products of oil sludge contributes to the reduction of firing temperature in comparison with clay samples without additives from 1150 to 1080 ?С. It is advisable to introduce pyrolysis products of oil-containing waste in the raw material mixture in the amount of up to 20 %.
