Volume 70, Nº 1 (2025)

The NaGdGeO₄, NaY_0.975Tm_0.025GeO₄, NaY_0.975Bi_0.025GeO_4, NaY_0.875Bi_0.025Eu_0.1GeO₄ samples were synthesized by different methods. According to powder X-ray diffraction data, the germanates crystallize in orthorhombic system pr.gr. Pnma, Z = 4. The influence of synthesis conditions, particularly different annealing modes, on morphological and optical properties of the samples were evaluated. The luminescence properties of NaY_0.975Tm_0.025GeO₄, NaGdGeO₄ and NaY_0.975Bi_0.025GeO₄, NaY_0.875Bi_0.025Eu_0.1GeO₄ compounds were studied in the near infrared range (1100 – 2100 nm, λ_ex = 808 nm), in the UV region (300–320 nm, λ_ex = 257 nm) and in the UV and visible wavelength range (300 – 700 nm, λ_ex = 298 nm), respectively. The influence of annealing parameters on the persistent luminescence duration of the last compositions was investigated additionally.

Promising for inorganic luminophores, terbium-doped lanthanum metaphosphates La_1-xTb_xP₃O₉ (x = 0.05, 0.1, 0.2, 0.3, 0.4) were synthesised by extraction-pyrolytic method at low temperature in comparison with known methods. The crystal structure and optical properties of the obtained samples were characterised by X-ray phase analysis, IR and luminescence spectroscopy, and the unit cell parameters were calculated. Сompounds having rhombic structure, pr. gr. C 222 ₁, were obtained in the temperature range of 500–900°C. All parameters of the unit cell decrease linearly with the introduction of terbium into lanthanum metaphosphate. La_1-xTb_xP₃O₉ compounds show intense luminescence in the region of 450–650 nm. The La_0.8Tb_0.2P₃O₉ sample obtained in one hour annealing at pyrolysis temperature of 900°C shows maximum luminescence intensity.

This study presents the synthesis and characterisation of lithium nickelate LiNiO₂ with near-stoichiometric composition prepared by a combined method. LiNiO₂ exhibits high electrochemical properties including a theoretical capacity of 250–270 mA/g, making it a promising cathode material for lithium-ion batteries as an alternative to LiCoO₂. However, the commercial use of LiNiO₂ is limited by the difficulty in achieving stoichiometric composition and the high cost of conventional synthesis methods. Using X-ray phase analysis and spectrometry, we identified the phases formed and determined their chemical composition. Electron microscopy and Brunauer-Emmett-Teller (BET) techniques were used to investigate the structure and morphology. The developed process scheme led to the preparation of lithium nickelate with the composition Li_(0.98)Ni_(1.02)O₂, providing the formation of nanoscale samples with high specific surface area and improved electrochemical performance. These results emphasise the potential of LiNiO₂ as a competitive cathode material for lithium-ion batteries.

For the first time in the coordination chemistry of palladium, a new class of palladium(I) polymers with unsaturated monocarboxylic acids obtained by the interaction of palladium(II) acetate Pd₃(μ-MeCO₂)₆ with monocarboxylic 3-pentenoic and 4-pentenoic acids with a double bond not conjugated with the carboxyl group, cinnamic and crotonic acids with a double bond conjugated with the carboxyl group was isolated, and the interaction with a dicarboxylic acid (itaconic) with a double bond conjugated with only one carboxyl group, similar to cinnamic and crotonic acids, was studied. Analysis of the composition of eight newly synthesized compounds, as well as their IR, Raman and EPR spectra showed that the obtained coordination polymers of Pd(I) [Pd(RCOO)₆]_n with 3-pentenoic {[Pd(π-C₅H₇O₂)] ∙ H₂O}_n and 4-pentenoic [Pd(π-C₅H₇O₂) ∙ C₅H₈O₂)]_n acids are diamagnetic, and with cinnamic [Pd(C₉H₇O₂)]_n, crotonic {[Pd(C₄H₅O₂)]H₂O}_n and itaconic {[Pd(C₅H₄O₄)H₂O] ∙ 2H₂O}_n acids they are paramagnetic. The backbone of the obtained polymers is formed by bridging carboxylate groups and Pd–Pd bonds. The completion of the coordination polyhedron in the case of complexes with 3- or 4-pentenoic acid is carried out by coordinating their double bond with palladium, in polymer complexes with cinnamic and crotonic acids - by the formed agostic bond, in complexes with itaconic acid - by a coordinated water molecule. According to EPR spectroscopy, the polymer with itaconic acid contains paramagnetic centers characterized by a content of 10¹⁸ spin/g of unpaired electrons stable for a year, which allows it to be considered as a precursor for the creation of heterogeneous catalysts with increased catalytic activity.

Using DFT calculations, the possibility of stabilizing the hexagonal honeycomb shape of borophene by mixed doping in the B₆Ga₂Mg₄ system was showed, where a flat sheet of borophene is placed between two layers formed by magnesium and gallium atoms. B₆Ga₂Mg₄ is a relatively soft material with metallic conductivity. Evaluation of the thermodynamic stability of this compound shows that melting will occur at temperatures above 1200 K.

Phase formation in the CuO–CO₂–H₂O–NH₃ system has been studied using thermodynamic modelling in the temperature range of 20–100°C, р^o = 0.1 MPa and ammonia concentrations of 0, 0.01 and 2.0 mol/kg. The stability fields of tenorite [CuO], malachite [Cu₂CO₃(OH)₂], azurite [Cu₃(CO₃)₂(OH)₂] were determined and the compositions of the solutions in equilibrium with the solid phases were calculated. The effect of temperature and ammonia concentration on the change in phase relations in the system was shown. It was found that during the interaction of tenorite, malachite and azurite with ammonia solutions 1.0–3.0 mol/kg, the copper content in the solution increased with increasing ammonia concentration and decreased with increasing temperature. The results presented provide a basis for understanding the mechanism of mineral formation in aqueous copper-carbonate systems, as well as for solving a number of environmental problems and developing technological processes for ammonia leaching.

Experimental data on the thermal stability and fluorinating ability of cerium(IV) fluoride are critically reviewed. From experiments on the joint fluorination of CeF₃k and platinum, the value Δ_fH°(CeF₄, k, 298 K) = –1939.9±7.6 kJ/mol was determined. The most reliable value of the enthalpy of sublimation of cerium tetrafluoride Δ_sH°(CeF₄, 298 K) = 270.2±1.7 was selected and Δ_fH°(CeF₄, g, 298 K) = –1669.6±7.8 kJ/mol was calculated. A comparison of CeF₄(k) with other solid-phase fluorinating agents was carried out.

The regularities of the sorption extraction of indium from sulfuric acid solutions using composites based on activated carbons modified with carbon nanotubes are considered. Their surface was studied by scanning electron microscopy. The equilibrium and kinetic characteristics of the sorbents are obtained. Indium sorption isotherms have a convex shape and are described by the Langmuir equation. The approximation of kinetic data using pseudo-first and pseudo-second order models, internal diffusion, and Elovich showed that the highest correlation coefficient is observed when using a pseudo-second order model. The process of indium sorption is limited by external diffusion. The efficiency of the carbon composite during the extraction of indium in four sorption-desorption cycles has been verified.