The synthesis of β-Ga₂O₃ ceramic was achieved using high-energy electron beams for the first time. The irradiation of gallium oxide powder in a copper crucible using a 1.4 MeV electron beam resulted in a monolithic ceramic structure, eliminating powder particles and imperfections. The synthesized β-Ga₂O₃ ceramic exhibited a close-to-ideal composition of O/Ga in a 3:2 ratio. X-ray diffraction analysis confirmed a monoclinic structure (space group C2/m) that matched the reference diagram before and after annealing. Photoluminescence spectra revealed multiple luminescence peaks at blue (~2.7 eV) and UV (3.3, 3.4, 3.8 eV) wavelengths for the synthesized ceramic and commercial crystals. Raman spectroscopy confirmed the bonding modes in the synthesized ceramic. The electron beam-assisted method offers a rapid and cost-effective approach for β-Ga₂O₃ ceramic production without requiring additional equipment or complex manipulations. This method holds promise for fabricating refractory ceramics with high melting points, both doped and undoped.

The use of CH₄ as an energy source is increasing every day. To increase the efficiency of CH₄ combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH₄ concentration in the exhaust gases of combustion systems. To this end, sensors are required that can withstand extreme operating conditions, including temperatures of at least 600 °C, as well as high pressure and gas flow rate. ZnGa₂O₄, being an ultra-wide bandgap semiconductor with high chemical and thermal stability, is a promising material for such sensors. The synthesis and investigation of the structural and CH₄ sensing properties of ceramic pellets made from pure and Er-doped ZnGa₂O₄ were conducted. Doping with Er leads to the formation of a secondary Er₃Ga₅O₁₂ phase and an increase in the active surface area. This structural change significantly enhanced the CH₄ response, demonstrating an 11.1-fold improvement at a concentration of 10⁴ ppm. At the optimal response temperature of 650 °C, the Er-doped ZnGa₂O₄ exhibited responses of 2.91 a.u. and 20.74 a.u. to 100 ppm and 10⁴ ppm of CH₄, respectively. The Er-doped material is notable for its broad dynamic range for CH₄ concentrations (from 100 to 20,000 ppm), low sensitivity to humidity variations within the 30–70% relative humidity range, and robust stability under cyclic gas exposure. In addition to CH₄, the sensitivity of Er-doped ZnGa₂O₄ to other gases at a temperature of 650 °C was investigated. The samples showed strong responses to C₂H₄, C₃H₈, C₄H₁₀, NO_2, and H₂, which, at gas concentrations of 100 ppm, were higher than the response to CH₄ by a factor of 2.41, 2.75, 3.09, 1.16, and 1.64, respectively. The study proposes a plausible mechanism explaining the sensing effect of Er-doped ZnGa₂O₄ and discusses its potential for developing high-temperature CH₄ sensors for applications such as combustion monitoring systems and determining the ideal fuel/air mixture.

The optical and vibrational responses of Gd₃Ga₅O₁₂ (GGG) single crystals to 147 MeV Kr-ion irradiations were systematically investigated to clarify defect formation pathways and their influence on luminescence mechanisms. Absorption spectra measured at room temperature reveal a stepwise redshift of the fundamental edge and the progressive development of a broad sub-band-gap tail between 4.4 and 5.3 eV, indicating the accumulation of F- and F⁺-type oxygen-vacancy centers and increasing structural disorder. Raman spectroscopy shows that, despite substantial track overlap at fluences up to 10¹⁴ ions/cm², the crystal preserves its phonon frequencies and linewidths, while peak intensities decrease due to a growing disordered volume fraction. Low-temperature (13 K) photoluminescence demonstrates the persistence of a dominant broad band near 2.4 eV and the emergence of an additional irradiation-induced band at ~2.75 eV whose width increases with fluence, reflecting the formation of vacancy-related defect complexes. Excitation spectra transform from band-edge-dominated behavior in the pristine crystal to defect-tail-mediated excitation in heavily irradiated samples. These results provide a consistent spectroscopic picture of ion-track-induced disorder in GGG and identify the defect states governing its luminescence under extreme irradiation conditions.

В работе исследованы радиационно-индуцированные структурные изменения в монокристаллах рутила TiO2 после облучения ионами 147 МэВ Kr до флюенсов 1011 и 1013 ион/см2. Методом рентгеноструктурного анализа установлено, что во всем исследованном диапазоне флюенсов сохраняется тетрагональная структура рутила без признаков фазового перехода. Показано, что при флюенсе 1011 ион/см2 изменения положения и формы дифракционных максимумов минимальны, что свидетельствует о высокой радиационной стойкости кристаллической решетки TiO2. При увеличении флюенса до 1013 ион/см2 наблюдается смещение рефлексов (110) и (220) в область меньших углов, указывающее на радиационно-индуцированное увеличение межплоскостных расстояний и расширение решетки рутила. Анализ параметров элементарной ячейки показал увеличение эффективного объема до ~3.6 % для основной компоненты и до ~8.3 % для поврежденного приповерхностного слоя. Рассчитанные значения микродеформации и эффективного напряженного состояния свидетельствуют о формировании неоднородного дефектного слоя с высокими локальными растягивающими напряжениями. Установлено, что основным эффектом воздействия быстрых тяжелых ионов является накопление радиационных дефектов, развитие напряженно-деформированного состояния и формирование поврежденного приповерхностного слоя без разрушения исходной структуры рутила TiO2. Полученные результаты представляют интерес для применения TiO2 в радиационно-стойких функциональных материалах и элементах ядерной и космической техники. Ключевые слова: TiO2, рутил, тяжелые ионы, радиационные дефекты, латентные треки, рентгеноструктурный анализ, микродеформация, радиационная стойкость.

The intrinsic defect-related luminescence of as-grown Gd₃Ga₅O₁₂ (GGG) single crystals was investigated using synchrotron excitation in the vacuum-ultraviolet region. The photoluminescence spectrum at 7 K exhibits a broad emission band centered near ~2.5 eV (≈500 nm), accompanied by narrow 4f–4f transitions of uncontrolled Tb³⁺ impurity ions. Gaussian decomposition of the broad band reveals three components at approximately 3.05, 2.70, and 2.50 eV, attributed to self-trapped excitons (STE), antisite-associated recombination, and F/F⁺-type oxygen-vacancy centers, respectively. Temperature-dependent photoluminescence measurements show that the defect-related luminescence is governed by two thermally activated nonradiative channels with activation energies of ~5–8 meV and 42–56 meV. The shallow channel dominates at 20–50 K, while the main quenching occurs between 100 and 150 K, leading to nearly complete suppression of the broad emission at room temperature. The present results therefore characterize the emission behavior of intrinsic, shallow defect centers in as-grown GGG and contribute to understanding defect recombination pathways that are critical for optimizing garnet-based scintillation and photonic materials.

This article examines the influence of unintentional Cr3+ and Fe3+ impurity ions on the luminescent properties of Gd3Ga5O12 (GGG) single crystals. The characteristic features of the spectra excited by high-energy syn chrotron radiation in the temperature range of 10–300 K are analyzed. It is shown that at 10 K the lumines cence is dominated by a narrow-band emission of Cr3+ ions arising from the spin-forbidden 2E→4A2 transi tion, which indicates weak electron–phonon coupling and high crystalline homogeneity. It is revealed that with increasing temperature the intensity of this transition decreases significantly, while a broadband lumi nescence emerges, associated with the spin-allowed 4T2→4A2 transition and the contribution of Fe3+ ion emis sion. The temperature evolution of the spectra is shown to result from thermal redistribution of the Cr3+ excit ed-state populations, interlevel state mixing, and partial removal of the spin-forbidden nature of Fe3+ transi tions due to lattice vibrations. Based on the study, conclusions are drawn regarding the role of impurity cen ters in energy transfer and nonradiative relaxation processes. The results are of interest both for fundamental photonics and for the development of efficient luminescent materials and optical devices designed to operate over a wide temperature range.