Optical/THz properties of thin gold films are controlled by the temperature of substrate during deposition. In the visible range the transmission spectra show the transmission of films deposited at elevated temperatures is reduced due to absorption and scattering of light energy on surface plasmons excited in gold nanograins that make up the nanofilm at high synthesis temperatures. In the infrared range, the situation is reversed. The transmission steadily grows with the film synthesis temperature because of the decrease of the intraband Drude absorption occurring due to the presence of boundaries between nanograins. In the THz range the transmission of gold film sharply increases as the films synthesis exceeds 200 degrees C, while the reflectivity exhibits sharp growth as the synthesis temperature is getting lower than 300 degrees C. The interference fringes in the THz radiation allow to establish the Sellmeier-type equation for fused silica in the THz range. On the whole, the study detailedly tracks the changes in optical properties of golden films deposited onto fused silica on the temperature of substrate during deposition. We show the extent of the control of optical properties in a wide spectral range from UV to THz for a certain film/substrate combination that is an important component of optical systems and instrumentation.

Zero-dimensional Bi 3+ /Sb 3+ alloying hybrid metal halides are developed to achieve tunable single-component white-light emission for sustainable solid-state lighting.

Developing blue-light-excitable narrow-band green-emitting materials is crucial for next-generation backlight displays. Here, we designed and synthesized a novel 0D hybrid bismuth halide, (OfloH2)2Bi2Cl10 & centerdot;3H2O (OBCH), using optically active ofloxacin (OFL) as the organic component. Under blue excitation, it exhibits bright narrow-band green-emission peaks at 515 nm. Although OBCH retains the intrinsic green emission originating from protonated OFL solution, its fluorescence exhibits a narrowed FWHM of 59 nm, attributed to enhanced structural rigidity resulting from the rigid bismuth halide framework and the layered stacking of organic cations. Benefiting from its strong blue light excitation, narrow FWHM, a stable white light-emitting diode device was fabricated by combining the 460 nm blue InGaN LED chip, green-emitting OBCH, and red-emitting KSF: Mn4+ with a luminous efficiency of 92.34 lm/W and a wide color gamut of 109.2% sRGB standard. This work not only provides a universal strategy for utilizing rigid and stable metal halide lattices as "reactors" to confine and modulate the photophysical behavior of organic luminophor, thereby unlocking superior performance unattainable in their free state, but also offers new insights for designing next-generation high-performance luminescent materials.

Cobalt-containing borates are emerging as multifunctional materials for optical devices, Li-ion and Na-ion battery anodes, and rare-earth-free permanent magnets. In particular, the phases Co2B2O5, Co3B2O6 and Co3BO5 - which incorporate Co2+ and Co3+ centers - can all be crystallized from closely related Bi2O3-MoO3-Na2O-B2O3 fluxes with only minimum compositional adjustments. In this study, we elucidate (1) high-temperature crystallization pathways in these multicomponent flux systems and (2) factors that stabilize Co in oxidation states +2 versus +3. By systematically varying the Na2O/MoO3/B2O3 ratio, we tune relative populations of Co2+- and Co3+-bearing species in the flux. We monitor the competitive formation of intermediate phases - Na2MoO4, CoMoO4, Na2B4O7 and putative NaCoO2 - and show how these intermediates direct the ultimate borate phase. Moreover, by incrementally introducing NiO into the flux, we estimate solid solutions of the kotoite type (Co3-xNixB2O6) and ludwigite type (Co3-xNixBO5) and map their phase boundary in unprecedented detail. This compositional "switch" controls whether Co3+-rich borates are formed. We report the first synthesis of Co3-xNixB2O6 solid solutions within the range of 0 < x < 1, which has not been previously explored, revealing a magnetic ordering transition near 35 K. Crystals of Co2B2O5 (pyroborate) and Co3-xNixBO5 ludwigites have also been grown. Comprehensive structural refinements and magnetic measurements of all the phases are presented to substantiate our mechanistic insights.

Zero-thermal-expansion (ZTE) materials are critical for stabilizing device performance under thermal fluctuations. Traditionally, achieving enhanced thermal stability has required three-dimensional (3D) ZTE, a stringent condition that severely limits material availability. Here, we show that low-dimensional ZTE can be realized in single crystals by orienting ubiquitous bond rotations along specific crystallographic axes in the framework structures, thus relaxing the strict requirements for 3D ZTE. This approach enables a two-dimensional ZTE response, as demonstrated in a trigonal YAl3(BO3)4 (YAB) crystal, which exhibits an ultralow thermal expansion coefficient of -0.02(7) MK-1 within the ab plane from 83 to 180 K. The practical impact of this low-dimensional ZTE is evidenced by the thermo-optical performance of YAB crystal: within the ZTE temperature range, the thermo-optical coefficient varies by only 0.03(2) × 10-8 K-2 in the ZTE plane, approximately two orders of magnitude lower than those of conventional optical materials. This study establishes a new design strategy for functional ZTE materials and highlights the application potential of dimensionally confined ZTE effects in precision optical and electronic devices.

FexCo3-xO4 nanoparticles (NPs) with x varied from 0.55 to 1.0 were synthesized by the auto-combustion method and subjected to the thermal treatment at different temperatures, Ttreat, (400–900 °C) and durations (1, 12, 24 h). An exceptionally strong impact of Ttreat on size, morphology and magnetic properties of NPs was revealed. The NPs average size increased by one to two orders of magnitude at Ttreat = 800–900 °C, which was associated mainly with the sintering process. Room temperature magnetization dependences on an external magnetic field were described by narrow hysteresis loops with the saturation magnetization Ms increasing strongly with an increase of x and Ttreat and low room temperature coercivity Hc increasing strongly with a decrease of the measurement temperature. The magnetic ions distribution over the crystal positions was probed with Mössbauer spectroscopy. To explain the peculiarities of the magnetic properties of the studied NPs and to correlate them with the distribution of magnetic ions over the crystal positions, we assumed the possibility of a transition of Co3+ ions from a low-spin to a high-spin state due to the distortion of the crystal field when replacing Co3+ ions with Fe3+ ions in octahedral positions. The intense MCD peak, centered near 1.85 eV, coincides in energy with the radiation of solid-state red lasers widely used in the NPs medical applications.

The cubic Fe2-xMnxO3 is an intriguing material that has recently been investigated for various applications, including lithium-ion battery anodes, catalysts, energy storage media, humidity sensors, and photocatalysts. Despite its wide range of promising applications, the magnetic properties of Fe2-xMnxO3 remain controversial, with different sources reporting conflicting information regarding the type of magnetic ordering, phase transition temperature, and magnetic moment of this compound. This work presents a study of the magnetic state of three Fe2-xMnxO3:Ga solid solutions with varying Mn:Fe:Ga ratios, along with one gallium-free Fe2-xMnxO3 reference sample. We performed a detailed analysis of the actual chemical composition and crystal structure of the synthesized samples using energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS) to evaluate compositional differences. The magnetic states of the three Fe2-xMnxO3:Ga samples and the gallium-free Fe2-xMnxO3 were investigated using magnetometry and Mossbauer spectroscopy. The low-temperature magnetic anomalies were found to be more consistent with spin-glass-like freezing than with conventional long-range antiferromagnetic ordering. Although variations in magnetic behavior were observed and found to depend on composition and the cooling rate during synthesis, our results demonstrate that these factors do not account for the drastically different magnetic properties reported for similar bixbyite-type oxides. Instead, the apparent room-temperature ferrimagnetism observed in one sample is most likely extrinsic and can be attributed to a trace spinel-type impurity phase, as supported by magnetizations and ESR measurements. Thus, the origin of these discrepancies lies primarily in the chemical purity of the samples and, to a significant extent, in the synthesis technique employed.

Asymmetric deconvolution of DTG curves was applied to separate overlapping decomposition stages of samarium polysulfide samples SmS2-x (S/Sm = 1.90-1.76). The Fraser-Suzuki function statistically outperforms symmetric models and the bi-Gaussian distribution (by AIC and BIC criteria). Rietveld refinement establishes that the studied samples are not continuous solid solutions but multiphase mixtures of discrete SmnS2n-1 homologues (P42/n). The S/Sm = 1.90 sample is predominantly ordered Sm10S19 (V = 1224 & Aring;3), while the 1.86-1.76 series comprises mixtures of Sm5S9 (V = 1267 & Aring;3) and Sm7S13 (V = 1243 & Aring;3) with lamellar morphology that promotes surface oxidation. In the multiphase samples, a structural relaxation stage (480-550 degrees C) was detected that is absent in ordered Sm10S19. Despite differences in initial phase composition and synthesis history, decomposition trajectories of all samples converge to a single intermediate Sm4S7 (SmS1.75) - the stoichiometric convergence effect. Under dynamic open-system conditions, the stepwise phase sequence predicted by the equilibrium diagram is not kinetically resolved. Instead, dissociation proceeds as a merged continuous process to the metastable Sm4S7 intermediate, which decomposes 120 degrees C below the closed-system equilibrium boundary. Diffuse reflectance spectroscopy reveals a multiband electronic structure with direct bandgaps of 1.89-2.00 eV. In multiphase samples, the Kubelka-Munk function acquires an Urbach tail, linking the coexistence of homologous phases to enhanced structural disorder in the optical response.

Isotropic zero thermal expansion (ZTE) materials are essential for applications requiring extreme dimensional stability, yet their operation is typically limited to narrow temperature windows below 400 K. Here we report the incorporation of flexible interstitial groups via fractionally occupied atoms into a closed-framework sodalite structure (Cd4Al6O12SO4, CASO). This material exhibits isotropic ZTE, with a thermal expansion coefficient of 0.21(23) × 10-6 K-1 from 11 K to 893 K. The high-temperature ZTE behaviour originates from the preserved transverse vibrations that drive negative thermal expansion-arising from the enhanced vibrations of positionally disordered ligand atoms-which effectively counterbalance the intrinsic positive thermal expansion. Moreover, CASO maintains structural integrity up to 1,100 K, features a solar-blind ultraviolet transparency window down to 275 nm and exhibits thermally induced optical fluctuations at least twice as low as those of conventional optical materials. This work provides both a high-performance crystal for extreme thermal environments and a strategy for designing wide-temperature-range ZTE materials.

The traditional solid-state synthesizing method was employed to prepare Tl5Yb1-xHoxZr(MoO4)6 (x = 0, 0.005, 0.1, 0.15, 0.3, 0.5) ceramics. Structural characterization was performed through the Rietveld method on the X-ray powder diffraction data. The unit cell parameters are defined for Tl5Yb1-xHoxZr(MoO4)6 (x = 0, 0.005, 0.1, 0.15, 0.3, 0.5). It was found that Tl5YbZr(MoO4)6 molybdate has average conductivity among all known molybdenum compounds (at T = 840 K – σ = 3.02 × 10−4 S / cm). The vibration spectra have been considered and analyzed for each new compound. The analysis reveals that the asymmetric ν3(F2) stretching vibration undergoes complete splitting. The upconversion findings show that there are three bands at 533–565 nm, 638–673 nm, and 745–765 nm, corresponding to transitions of Ho3+ ions from 5F4/5S2 to 5I8, 5F5 to 5I8, and 5F4/5S2 to 5I7 respectively.

Three polymorphs were found to exist for Cs3ScF6 in the room temperature range of up to 280 degrees C. Two phase transitions were identified by differential scanning calorimetry (DSC) analyses at 92 and 196 degrees C upon heating. In situ high-temperature solid-state NMR, synchrotron and laboratory X-ray diffraction, and neutron powder diffraction were used for structural characterization. The crystal structure of the high-temperature (gamma) phase adopts the cubic Fm3m (Z = 4) space group with a = 9.6048(7) & Aring; at 250 degrees C. The other two polymorphs, alpha and beta, have tetragonal symmetry with space groups I41/a (Z= 80) and I4/m (Z= 10), and lattice parameters are a = 21.15222(6) & Aring;, c = 38.21648(8) & Aring; and a = 15.0401(2) & Aring;, c = 9.6341(2) & Aring; at RT and 150 degrees C, respectively.

A series of single crystals of solid solutions KTi1-xZrxOAsO4 ( x = 0.025, 0.05, 0.075, 0.1) have been grown by the Czochralski method. The structural analysis of this series of samples showed that at titanium partial substitution (0.025 <= x <= 0.1) Zr4+ occupies the T1 position of the Ti1O6 octahedron, as well as the T2 position of the Ti2O6 octahedron, at the same time the volume of octahedra increases. But at 0.05 <= x <= 0.1 the volume of the Ti1O6 octahedron stops growing, and only the volume of Ti2O6 increases, consequently, at x = 0.05 Zr saturation is observed at position Ti1. The Raman spectrum of a pure KTA crystal is very different from the spectra of the entire range of solid solutions. In the transmission spectrum of samples with partial substitution of titanium atoms by zirconium atoms, there is practically no wide absorption band at 3.5-4 mu m typical for pure KTA, the maximum crystal transparency in this region is achieved for x = 0.075. It was found that the introduction of large Zr ions into the KTiOAsO4 structure leads to a distortion of the lattice and an increase of the band gap.

New structure of Na3Yb(BO3)2 has been synthesized for the first time using a solid-state reaction method. The crystal structure of the title compound was elucidated using a simulated annealing method. Samples used in powder diffraction analysis for structure determination were prepared via solid-state synthesis. To refine obtained crystal structure, the Rietveld method was applied, yielding the following parameters: triclinic symmetry (sp. gr. P 1.), a = 5.1661(1) angstrom, b = 6.6249(2) angstrom, c = 8.5991(2) angstrom, alpha = 92.089(1)degrees, beta = 93.281(2)degrees, gamma = 88.010(1)degrees, Z = 2, V = 293.47(1) angstrom 3, R wp = 4.83, GOF = 4.85. The double borate Na3Yb(BO3)2 congruently melted at 1119 degrees C exhibited a complex thermal profile, as evidenced by DSC, with four polymorphic transitions observed at 277 degrees C, 497 degrees C, 653 degrees C, and 694 degrees C. Ab initio calculated IR spectrum of Na3Yb(BO3)2, exhibited a high degree of agreement with the experimentally obtained IR spectrum. The band gap of the title compound was calculated to be 4.7(2) eV using the combination of the Tauc method and DASF method. The calculated energy barrier for sodium ion migration, equal to 0.5 eV, was in a reasonable agreement with the experimentally determined activation energy of 0.75 eV. The title compound exhibited an ionic conductivity of 0.4 x 10-3 S/cm at 1023 K.

Near-infrared (NIR) light has a high application value in various fields due to its spectral characteristics. Typically, the broadband NIR emission of Cr3+ is based on the transition of 4T2→4A2, while the 2E level emits narrowband emission. This work discovered broadband NIR emission from the [4A2, 4T2] coupling excited state energy level in the spinel structure. The dense and adjacent Al1O6 as the occupied sites of Cr3+ provides a structural basis for the exchange coupling effect under high Cr3+ concentration, as confirmed by the analysis of site occupancy, formation energy, bond valence sum, and effective coordination number. Spectral information and EPR signals indicate that the [4A2, 4T2] coupling excited state in the emission spectrum corresponds to the downward shift of the T2 energy level caused by the Cr3+-Cr3+ exchange coupling interaction in the strong crystal field of LAO:Cr3+. The internal and external quantum efficiencies of LAO:0.15Cr3+ are 80.6% and 30.3%, respectively. The luminescence intensity at 370 and 423 K is approximately 92% and 85% respectively of that at room temperature. The excellent luminescence thermal stability is attributed to the activation energy of 0.21 eV and the Huang-Rhys factor S = 3.95. Finally, the material was fabricated into pc-LEDs and its applications in night vision and plant lighting were explored.

Since catalytically active materials require special synthesis conditions, which cause difficulty in scaling, it is necessary to develop new lightweight scalable approaches for industrial applications. The most obvious way is to use elementary components to fabricate complex structures. In our work, we used a fundamental ampoule synthesis method to produce MSSe (M = Mo, W) powders with a homogeneous random distribution of chalcogen atoms. The synthesized samples exhibit P63/mmc space group indicating the existence of 2 H phase which was proved by comprehensive experimental and theoretical analysis and demonstrates rational characteristics in the hydrogen evolution reaction. The Tafel slopes for synthesized MoSSe and WSSe are 93 and 86 mV/dec, respectively. Moreover, the MSSe samples demonstrate the same catalytic activity in the hydrogen evolution reaction as the samples subjected to ultrasonic treatment in N-Methyl-2-pyrrolidone, with Tafel slopes of 92 and 88 mV/dec for MoSSe and WSSe, respectively.

This work encompasses the study of magnetic, optical, and structural properties of the coordination compounds [Ln(MeDPQ) 2 Cl 3 ] (Ln ─ Ho 3+ , Er 3+ , Dy 3+ , and Y 3+ ; MeDPQ − 2‐methyldipyrido‐[3,2‐f:2′,3′‐h]‐quinoxaline) and substituted complexes [Ln 1‐ x Dy x (MeDPQ) 2 Cl 3 ] (Ln = Ho 3+ , Er 3+ , and Y 3+ ) based on them. Magnetic measurements within the range 5–300 K revealed single ion anisotropy in [Dy(MeDPQ) 2 Cl 3 ], with the Curie‐Weiss temperature θ being −3.69 ± 0.03 K. Complexes of Ho 3+ and Er 3+ exhibited f – f emission in the visible range, while the latter was also emissive in the NIR. Dilution of the Dy 3+ complex with diamagnetic Y 3+ ions resulted in alterations of magnetic and photophysical properties. The substituted complexes Y 0.5 Dy 0.5 and Y 0.9 Dy 0.1 demonstrated paramagnetic behavior, with θ being 3.06 ± 0.12 K and 9.64 ± 0.23 K, respectively. In both cases, the emission decay times of Dy 3+ changed insignificantly, 21.02 ± 0.41 µs and 14.56 ± 0.22 µs, respectively, compared to the value (18.92 ± 0.03 µs) of the individual Dy 3+ complex. Additional ligand‐based emission bands were observed in the Ho 3+ and Er 3+ complexes at room temperature and 77 K and in the substituted complexes Ho 0.5 Dy 0.5 and Er 0.5 Dy 0.5 at room temperature, which were assigned to the exciplex states. The thermal stability of [Er 0.5 Dy 0.5 (MeDPQ) 2 Cl 3 ] was determined to be the same as for the individual complexes, starting to oxidize at 410°C.

-A new Sn3Mo2O8 compound was synthesized and its crystal structure was determined. A Sn3Mo2O8 / Bi26Mo10O69 (89 %/11 %) composite was obtained by the solid-state synthesis. Vibrational modes of octahedra and temperatures of softening and disappearance of some modes from the IR absorption spectra in the temperature range of 80-500 K and the frequency range of 350-7000 cm-1 was found. A correlation was established between the temperatures of the thermopower maxima and softening of IR modes, and anomalous in the temperature coefficient of resistance, impedance, which was explained within the displacement-type phase transition model. The activation energy and temperature range of the ionic conductivity in the Sn3Mo2O8 compound was determined.

New noncentrosymmetric molybdate Tm2Zr(MoO4)5 was synthesized. The crystal structure variation with temperature was determined by Rietveld analysis. At 303 K, the monoclinic structure was determined in space group P21. A reversible phase transition P21 <-> Cmc21 was found at 390 K. From 423 to 520 K, nearly a ZTE (alpha = 0.7 x 10-6 K-1) behavior was revealed. In the range of 520-720 K, the negative thermal expansion (NTE) effect (alpha = -2.3 x 10-6 K-1) is evident for the cell volume. Tm2Zr(MoO4)5 is stable up to 1100 K. Electronic structures of monoclinic and orthorhombic Tm2Zr(MoO4)5 were evaluated by DFT methods. The bandgap values determined for monoclinic Tm2Zr(MoO4)5 are Eg direct = 3.83 eV and Eg indirect = 3.43 eV. The vibrational properties of monoclinic phase were characterized by Raman spectroscopy. The photoluminescence emission in monoclinic Tm2Zr(MoO4)5 at 303 K is dominated by a narrower band at 650 nm due to the 1G4 - 3F4 transition.