A transparent Er³⁺,Yb³⁺:GdMgB₅O₁₀ single crystal with dimensions up to 24 × 15 × 12 mm was grown successfully by the high-temperature solution growth on dipped seeds technique from K₂Mo₃O₁₀-based solvent. The grown crystal was characterized using PXRD, DSC and ATR techniques. Differential scanning calorimetry measurements and SEM analysis of the heat-treated solids revealed Er,Yb:GdMgB₅O₁₀ to be an incongruent melting compound with an onset point of 1087 °C. The absorption edge of the Er,Yb:GMBO sample is located in the region of 245 nm, which approximates a value of 4.8 eV. Absorption and emission spectra, and luminescence kinetics, were studied. The energy transfer efficiency from ytterbium to erbium ions was determined. The laser operation in continuous-wave mode was realized and output characteristics were measured. The maximal output power of 0.15 W with a slope efficiency of 11% was obtained at 1568 nm.

TmMgB₅O₁₀ spontaneous crystals were synthesized via the flux-growth technique from a K₂Mo₃O₁₀-based solvent. The crystal structure of the compound was solved and refined within the space group P2₁/n. The first principles calculations of the electronic structure reveal that TmMg-pentaborate with an ideal not defected crystal structure is an insulator with an indirect energy band gap of approximately 6.37 eV. Differential scanning calorimetry measurements and powder X-ray diffraction studies of heat-treated solids show that TmMgB₅O₁₀ is an incongruent melting compound. A characteristic band of the Tm³⁺ cation corresponding to the ³H₆ → ¹D₂ transition is observed in the photoluminescence excitation spectra of TmMg-borate. The as-obtained crystals exhibit intense blue emission with the emission peaks centered at 455, 479, 667, and 753 nm. The most intensive band corresponds to the ¹D₂ → ³F₄ transition. TmMgB₅O₁₀ solids demonstrate the thermal stability of photoluminescence.

In this work, a unique technique for replicating the void structure of a low-permeability reservoir in a silicon microfluidic chip has been developed. This technique is qualitatively superior to all previous ones and provides full repeatability of key parameters of the void structure (permeability; pore size distribution; average channel diameter; channel tortuosity, macro- to microporosity ratio) from digital core data. Moreover, the developed technique allows to exactly copy the pore geometry of the core sample from micro-CT images and recreate it inside the microfluidic chip. Using this technique, three artificial void space structures were developed for three samples of Achimov sandstones with different permeability (0.38; 2.04 and 9.86 mD). The mineralogical composition of the prototype samples was determined by a set of lithological and mineralogical studies and a positive correlation between the intensity of carbonate cementation and the decrease in permeability was revealed. Most of the macropores in the studied sandstones are associated with leaching of feldspars, and micropores are confined mainly to clay minerals. The conducted set of studies on the present samples will make it possible to extend the results of future filtration tests to rocks with similar mineralogical characteristics and filtration-capacitance properties. A qualitatively new method of creating inhomogeneous wettability of artificially created void space structure inside the microfluidic chip was developed. This technique consists in a smooth displacement of formation water from the microchip structure by a hydrophobic agent, which modifies wettability on the surface of macropores and channels, but does not enter the micropore structure due to residual water, which is held inside the microporous structures by capillary forces. Thus, this work is the first to apply a comprehensive multidisciplinary approach to replicate the core void structure within a microfluidic chip. In the future, this technique will be improved so that the results of filtration tests on microfluidic chips will even more reliably reflect fluid movement within the reservoir.

Phase relationships in the Er_xYb_yY_1−x−yGa₃(BO₃)₄–Bi₂O₃–B₂O₃–(Y,Er,Yb)₂O₃–Ga₂O₃and Er_xYb_yGd_1–x−yGa₃(BO₃)₄–Bi₂O₃–B₂O₃–(Gd,Er,Yb)₂O₃–Ga₂O₃(x= 0.02,y= 0.11 at%) systems were studied in the temperature range from 1000 to 900 °C.

YGa₃(BO₃)₄ single crystals were grown from a K₂Mo₃O₁₀-based flux, and also RGa₃(BO₃)₄ (R = Y, Pr–Yb) spontaneous crystals (RGB) were obtained by a high-temperature flux growth technique from a complex R₂O₃–Bi₂O₃–B₂O₃–Ga₂O₃ solvent.

The structural origin of the germanate anomaly in glasses, which involves complex Ge–O coordination environments, is frequently studied using crystalline analogs. This study aims to provide reliable spectroscopic fingerprints by performing a detailed structural and thermal analysis of crystalline A₄Ge₉O₂₀ model systems with A = Li, Na, K. The compounds were synthesized via melt crystallization and characterized using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and Raman spectroscopy techniques. The results demonstrate clear cation-dependent crystallization pathways. The Li-containing system predominantly forms Li₂Ge₇O₁₅ in mixture with Li₄Ge₉O₂₀, indicating a preference for thermodynamically stable phases. The Na-system successfully yields the target Na₄Ge₉O₂₀ compound. In contrast, the K-system primarily produces the likely metastable K₂Ge₄O₉ phase with a significant amorphous fraction, highlighting the role of kinetic limitations. This comparative study demonstrates that the size of the alkali cation is a critical factor for controlling phase formation under identical stoichiometric and thermal conditions.