Perfect Crystal Research Articles

Perfect Crystals: microgravity capillary counterdiffusion crystallization of human manganese superoxide dismutase for neutron crystallography

The NASA mission Perfect Crystals used the microgravity environment on the International Space Station (ISS) to grow crystals of human manganese superoxide dismutase (MnSOD)—an oxidoreductase critical for mitochondrial vitality and human health. The mission’s overarching aim is to perform neutron protein crystallography (NPC) on MnSOD to directly visualize proton positions and derive a chemical understanding of the concerted proton electron transfers performed by the enzyme. Large crystals that are perfect enough to diffract neutrons to sufficient resolution are essential for NPC. This combination, large and perfect, is hard to achieve on Earth due to gravity-induced convective mixing. Capillary counterdiffusion methods were developed that provided a gradient of conditions for crystal growth along with a built-in time delay that prevented premature crystallization before stowage on the ISS. Here, we report a highly successful and versatile crystallization system to grow a plethora of crystals for high-resolution NPC.

Combing Seeding Crystallization with Flotation for Recovery of Fluorine from Wastewater: Experimental and Molecular Simulation Studies.

For effective removal and utilization of fluorine resources from industrial wastewater, stepwise removal and recovery of fluorine were accomplished by seeding crystallization and flotation. The effects of seedings on the growth and morphology of CaF2 crystals were investigated by comparing the processes of chemical precipitation and seeding crystallization. The morphologies of the precipitates were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) measurements. The seed crystal, fluorite, helps improve the growth of perfect CaF2 crystals. The solution and interfacial behaviors of the ions were calculated by molecular simulations. The existing perfect surface of fluorite was proven to provide the active sites for ion adhesion and formed a more ordered attachment layer than the precipitation procedure. The precipitates were then floated to recover calcium fluoride. By stepwise seeding crystallization and flotation, the products with a CaF2 purity of 64.42% can be used to replace parts of metallurgical-grade fluorite. Both removal of fluorine from wastewater and the reutilization of the fluorine resource were realized.

Effect of electron beam irradiation on thermal stability and crystallization behavior of flexible copolyester/multiwalled carbon nanotubes nanocomposites

AbstractPoly(butylene adipate‐co‐terephthalate) (PBAT), a biodegradable copolyester, was used as the polymer matrix to prepare nanocomposites with multiwalled carbon nanotubes (MWCNT) by melt‐mixing followed by hot‐pressing. The PBAT/MWCNT nanocomposites were exposed to electron beam (EB) irradiation, and thermal stability, melting and crystallization behavior of irradiated and unirradiated nanocomposites were comparatively investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. TGA results reveal increased thermal stability (up to 17°C) and maximum degradation temperature (Tmax) (up to 15°C) of PBAT/MWCNT nanocomposites, attributed to the high thermal stability of MWCNT and good MWCNT–PBAT interfacial interactions. However, the activation energy for thermal degradation (Ea) decreased with the presence of MWCNT in comparison to neat PBAT regardless of the MWCNT concentration. Both the thermal stability and Tmax of irradiated nanocomposites decreased by 3°C despite the crosslinking which can be attributed to successive minor irradiation‐induced polymer degradation, while Ea remained unchanged. Declined melting temperature (Tm), enthalpy of crystallization, enthalpy of melting and crystallinity of nanocomposites with the presence of MWCNT suggest the formation of less perfect crystals. Meanwhile, their increased glass transition temperature (Tg) and crystallization temperature (Tc) are due to the increased rigidity of PBAT chains and a reduced crystallization process in the presence of MWCNT, respectively. Similarly, reduced crystallinity and values of Tm and Tc of EB‐irradiated nanocomposites by 4.1%, 9.6%, and 7.5%, respectively, signifying the presence of PBAT‐crosslinks resulting in crystal defects.

Nucleation Retardation of Polyamide 6,6 by Tuning Hydrogen Bonding Reorganization via Nigrosine for High-Speed Injection Molding Applications

The mechanism of regulating hydrogen bond organization for polyamide 6,6 (PA 6,6) by nigrosine was investigated by temperature-dependent FTIR and in situ synchrotron X-ray diffraction during cooling/heating processes. The intermolecular interaction between amide groups and nigrosine was verified by the FTIR spectroscopy method. Upon melt cooling, the formation of H-bonds is promoted by nigrosine at the initial stage (regime I) with increased enthalpy change (ΔH1), which results from denser molecular coils as the interaction with nigrosine increases the ability to form H-bonds between adjacent amide groups, while at a lower temperature (regime II), the ΔH1 decreases with increasing nigrosine as nigrosine restrains the mobility of PA 6,6 chains that retards the formation of H-bonds between nonadjacent amide groups. Moreover, the ordering arrangement of H-bonds into 2-D hydrogen bond sheets (H-sheets) is hindered for both the regime I′/II′ stages with decreased ΔH2 due to the decreased mobility of chain segments, which retards the nucleation of PA 6,6 crystallization. The crystal perfection index (CPI) was investigated by WAXD, and it was found to decrease with the increase of nigrosine. Combined with microstructure analysis, we proposed that partial nigrosine can insert between H-sheets, which therefore tunes the Brill transition behavior of PA 6,6. Overall, the regulation mechanism of nigrosine on PA 6,6 crystallization has been established via interaction with amide groups to tune the organization of H-sheets. The retardation effects on crystallization can improve the flowability of PA 6,6 for high-speed injection molding applications.

Effects of cold storage temperature on thermoreversible aging in heavily oxidized asphalt binders

In order to better understand the thermoreversible aging characteristics of asphalt after heavy oxidation, six selected heavily oxidized asphalt containing different proportions of C20H42 are subjected to extended bending beam rheometer (ExBBR) tests, while modulated differential scanning calorimetry (MDSC) and atomic force microscope (AFM) are also performed on the asphalt. The results indicate that the introduction of heavy oxidation will not only affect the low temperature properties of the asphalt but also its thermoreversible aging characteristics, but this effect will receive an influence of the storage temperature. This is due to the increase in viscosity of the asphalt after heavy oxidation, which makes it difficult for C20H42 to migrate, while the increase in storage temperature can release the potential of the degree of thermoreversible aging of the asphalt by accelerating the movement of wax molecules. And like C20H42, the grade loss of asphalt blended with C30H62 is different at different storage temperatures and oxidation levels, which proves that for heavily oxidized asphalt, multiple storage temperatures should be selected for testing its grade loss. Combined with thermal and morphological analysis, the introduction of heavy oxidation not only increases the amount of wax precipitation, but also significantly increases the thermoreversible aging of the asphalt by lowering the Tg of the asphalt and forming more perfect crystals during low temperature storage. Finally, by comparing the grade loss due to cold storage and extended oxidation, it can be found that the incorporation of C20H42 will make the asphalt more influenced to physical hardening. Therefore, it is necessary to study the effect of asphalt wax content on the degree of thermoreversible aging of heavily oxidized asphalt.

High Curie Temperature in Epitaxial D022–Mn3−xGa Ultrathin Films

The D0[Formula: see text]–Mn3Ga ferrimagnet promises potential applications in spintronics due to its low magnetization, strong perpendicular magnetic anisotropy and high Curie temperature. In the form of thin and thick films, these properties are preserved. Here, we report on the structural and magnetic characterization of epitaxial D0[Formula: see text]–Mn[Formula: see text]Ga ultrathin films with thicknesses of 2[Formula: see text]nm, 5[Formula: see text]nm and 8[Formula: see text]nm grown on Cr buffer layers by magnetron sputtering. We found that the films are perfect single crystals with flat surfaces and Curie temperatures higher than 300[Formula: see text]K. The 2[Formula: see text]nm-thick ultrathin film has higher magnetization than that of the thicker films, likely due to uncompensated ferrimagnetic planes, along the c-axis, linked to the surface roughness at the atomic scale. These properties highly suit the requirements for the elaboration of spintronic devices such as magnetic tunnel junctions.

Effects of alloying elements on the super-lattice intrinsic stacking fault energy and ideal shear strength of Ni3Al crystals

The effects of alloying elements (Re,W,Ti,Ta,andMo) on the super-lattice intrinsic stacking fault energy and ideal shear strength (σmax) of Ni3Al crystals at 0 K was studied through first-principles calculation. The calculated formation enthalpy of point defects reveals that single solute atoms (i.e., Re,W,Ti,Ta,andMo) tend to occupy the Al site, while solute–solute complex defects (i.e., Re-Re, Re-W, Re-Mo, Re-Ta, Re-Ti, W-Mo, W-Ta, W-Ti, Mo-Ta, Mo-Ti, and Ta-Ti) tend to occupy the Al-Al site. The addition of single solute atom can increase the unstable stacking fault energy and ideal shear strength (σmax) of perfect Ni3Al crystals. Therefore, the doping of a single solute atom is beneficial for the creep strengthening of Ni3Al crystals. Compared with the doping of W,Ti,Ta,andMo, the doping of Re can more effectively impede the nucleation and movement of dislocations of Ni3Al crystals. Through the careful comparison of the creep properties of Ni3Al crystals with solute–solute complex defects, a conclusion can be drawn that the doping of alloy elements W and Re exhibit similar strengthening effects on the creep properties of Ni3Al crystals. W can be preliminarily predicted to replace part of Re in Ni3Al crystals without affecting creep properties. In addition, comprehensive evaluation reveals that the weak interaction between solute–solute complex defects should improve the strengths of Ni3Al crystals to a certain extent.

ИССЛЕДОВАНИЕ СТРУКТУРНОГО СОВЕРШЕНСТВА МОНОКРИСТАЛЛОВ И КЕРАМИК НИОБАТА И ТАНТАЛАТА ЛИТИЯ РАЗНОГО СОСТАВА И ТЕХНОЛОГИЙ ПО СПЕКТРАМ КОМБИНАЦИОННОГО РАССЕЯНИЯ СВЕТА ПЕРВОГО И ВТОРОГО ПОРЯДКОВ

The results of a study of the structural perfection of crystals and ceramics of lithium niobate and lithium tantalate of various compositions are presented. In solid solutions of the LiNbxTa1-xO3 family with 0.4 ≤ x ≤ 0.6, lines were found in the Raman spectra, both of the first (in the range of 150–900 cm–1) and of the second order, located in the range of 900–2000 cm–1. Second-order Raman lines in the range 900–2000 cm–1 were also recorded by us in single crystals of single-doped lithium niobate and lithium tantalate LiNbO3:Tb (2.24 wt. %), LiTaO3:Cr (0.005 wt. %), and double-doped lithium tantalate LiTaO3:Cr (0.2):Nd (0.45 wt. %). The observed lines in the range 900–2000 cm-1 are explained as a manifestation of overtone processes corresponding to biphonons.

Marangoni Flow Driven via Hole Structure of Soluble Acene–Polymer Blends for Selective Nitrogen Dioxide Sensing

AbstractThe correlations between semiconductor type and gas sensing properties in soluble acene/polymer blends have not yet been examined. Here, the phase separation mechanism in pseudo‐liquid phase blend film is investigated and an unusual solid‐state morphology that is effective for amperometric gas sensing performance is demonstrated. In 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS–pentacene)/poly(fluorine‐co‐triarylamine) (PTAA) blend, two phases are uniformly mixed, without being completely phase‐separated due to the similar solubility and surface tension. On the other hand, in 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl) anthradithiophene (diF–TES ADT)/PTAA blend, the diF−TES ADT molecules are segregated both at the air–film, and film–substrate interfaces, and subsequently crystallized with a high degree of crystal perfection. In the meanwhile, Marangoni‐flow induces crater‐like via hole structure of PTAA at the middle layer. In situ measurement of (ultraviolet–visible) UV–vis absorption spectra and computational calculation reveal kinetics of liquid–solid–crystal transition in relation to the functional groups of soluble acene. Interestingly, flow driven hole structure of PTAA in diF–TES ADT/PTAA blend film allows the target NO2 gas to selectively penetrate the channel region, thereby enhancing sensitivity toward NO2, while decreasing affinity with other gases. The results provide protocols for fabricating highlperformance field‐effect transistors and gas sensors in a blending system.

Single crystal of CsLiMoO4: Growth by low-temperature-gradient Czochralski technique, thermodynamic characteristics

For the first time, single crystal of CsLiMoO4 was grown by low-temperature-gradient Czochralski technique with weight control. The low-temperature-gradient Czochralski technique is technique that allows one to grow the most perfect crystals. It was shown that structure of CsLiMoO4 single crystal was cubic. Thermodynamic properties of CsLiMoO4 single crystal, which were necessary for optimizing the conditions of crystal growth, developing recommendations for its application in optoelectronics, microelectronics, electro-optics, in investigations of rare events and other areas, were studied by calorimetry methods. For the first time, the standard formation enthalpy was obtained by reaction calorimetry; lattice enthalpy and stabilization energy of CsLiMoO4 single crystal was calculated. It was shown that single crystal was thermodynamically stable with respect to decomposition into simple oxides at room temperature. Based on obtained and published data, it was shown that with decreasing of lattice enthalpies, the luminescence length decreasing in series Li2MoO4-CsLiMoO4-Cs2MoO4, which is very important to study rare events, applications in optoelectronics and etc. The heat capacity of CsLiMoO4 single crystal was measured for the first time by differential scanning calorimetry in the temperature range of 320–1000 K. It was shown that there were no phase transitions for CsLiMoO4 single crystal in this temperature region, which made it promising for application in this temperature range.

Role of temperature and preexisting dislocation network on the shock compression of copper crystals

Shock wave experiments show that many annealed face-centered cubic metals exhibit an anomalously increasing yield strength with temperature at high strain rates. Such an increase is usually associated with the multiplication of dislocations in the phonon friction mode, which slows with temperature. However, the effect of temperature on the structure of the shock wave and the yield strength of metal crystals, including those with microstructure, remains elusive. In this paper, we perform molecular dynamic simulations of shock-wave loading for [110] and [111] copper crystals of 0.45 and 0.80μm length in a wide range of temperatures between 100 and 1100K to understand the role of temperature and preexisting dislocations on the Hugoniot Elastic Limit (HEL). We show that, in ideal copper crystals, the elastic precursor exhibits a form of plateau, and the HEL almost does not change with shock propagation distance. However, at higher impacts, the perturbations of an elastic precursor are observed leading to fluctuations in the HEL value. We show that temperature dependencies of the HEL are strongly anisotropic. The HEL values tend to decrease with temperature for [110] perfect copper crystals, and to increase with temperature for [111] copper crystals. This surprising result is explained by the presence of dislocation substructures in a plastic wave in [110] crystals, which reduces the mobility of dislocations and makes the process of dislocation nucleation more dominant than in [111] crystals. Preexisting dislocations in copper crystals allow the HEL to decay much faster than in ideal crystals. In contrast to ideal [110] crystals, [110] crystals with dislocations exhibit increasing HEL values with temperature, as do [111] crystals. We find that the HEL dependence could be well approximated by a power law, but the decay power changes as the wave propagates. The decay power values lie between 0.5 to 0.7 in the second stage for both [110] and [111] crystals, which is consistent with experimental results with polycrystalline annealed copper. Our findings extend our understanding of temperature-dependent mechanical properties of materials under high strain rate and crystal plasticity.

Organic heterostructured scintillators with a high pulse shape discrimination capability

Recently, we have developed a new type of the scintillation material, namely organic composite scintillators. It is a non-scintillating transparent gel composition (a polysiloxane elastomer) containing grains of organic single crystals. The grains are obtained after directional crystallization of the material by crushing a crystalline ingot under a layer of liquid nitrogen. This approach removes technological restrictions on the area of the entrance window of a scintillator, does not require the growth of structurally perfect single crystals and their subsequent mechanical treatment. In contrast to organic single crystals and liquids, these materials are not continuous media but heterostructured ones.The ability of single crystals and liquids to separate signals from radiations with different specific energy losses dE/dx is well known. Due to the peculiarities of the creation and recombination of triplet-excited (T) states in these objects is also well studied. Such information on heterostructured scintillation materials, for which the grain size can limit migration of T-states, is practically absent.We discuss the results of the investigation of the luminescence spectra upon excitation by light into the T-states absorption region and the relative light yield of composite scintillators containing p-terphenyl grains (both activated and non-activated) and trans-stilbene grains. We used the grain fractions from 0.04 to 1.0 mm. We obtained and studied both single-layer samples (the thickness of a sample practically corresponded to the grain size of the scintillation material) and samples of 5 mm thick. The research results showed that samples with grain fractions of less than 0.04, 0.06 and between 0.06 and 0.1 mm have low intensity of the delayed fluorescence and relative light output values. We obtained that to separate radiations with different dE/dx by the shape of the radioluminescence pulse it is advisable to use grain fractions larger than 0.1 mm. We also discuss the physical processes that can lead to such results.

Initial Response of Pentaerythritol Tetranitrate (PETN) under the Coupling Effect of Preheating, Shock and Defect via the Molecular Dynamics Simulations with the Multiscale Shock Technique Method.

The initial response of PETN under the coupling of preheating, impact and defects was simulated by Multiscale Shock Technique (MSST) method and molecular dynamics. The temperature change of PETN during impact compression can be divided into three stages: (1) the elastoplastic change of the system caused by initial compression; (2) part of PETN decomposes and releases energy to raise temperature; (3) a secondary chemical reaction occurs, resulting in rapid temperature rise. Under the given conditions, a higher initial preheating temperature will lead to faster decomposition of PETN; The existence of defects will accelerate the decomposition of PETN molecules; Coupling the highest preheating temperature with defects will lead to the fastest decomposition of PETN molecules, while in the defect-free PETN system with a preheating temperature of 300 K, the decomposition of PETN molecules is the slowest. For the case of Us = 8 km·s-1, the effect of defects on the initial PETN reaction is greater than the initial preheating temperature; When the impact velocity is greater than 9 km·s-1, the impact velocity is an important factor affecting the decomposition of PETN molecules. For Us = 10 km·s-1, NO2 is the main initial product in the defective PETN crystal, while in the perfect PETN crystal, it is the combination of NO2 and HONO. The chemical reaction kinetics analysis shows that the preheating temperature and defects will accelerate the decomposition of PETN. The higher the preheating temperature, the faster the decomposition of PETN. For the case of Us = 7 km·s-1, 8 km·s-1 and 9 km·s-1, the existence of defects will increase the decomposition rate by more than 50% regardless of the initial preheating temperature. In the case of Us = 10 km·s-1, the improvement of decomposition rate by defects is not as significant as the initial preheating temperature.

Towards to solution of the fractional Takagi–Taupin equations. The Green function method

Developing the comprehensive theory of the X-ray diffraction by distorted crystals remains to be topical of the mathematical physics. Up to now, the X-ray diffraction theory grounded on the Takagi–Taupin equations with the first-order partial derivatives over the two coordinates within the X-ray scattering plane. In the work, the theoretical approach based on the first-order fractional Takagi–Taupin equations with the ‘quasi-time variable’ of the order $$\alpha \in (0,1]$$ along the crystal depth has been suggested and the corresponding X-ray Cauchy issue is formulated. Accordingly, using the Green function method in the scope of the Cauchy issue, the fractional Takagi–Taupin equations in the integral form have been derived. In the case of the inhomogeneous incident X-ray beam, the solution of the Cauchy issue of the X-ray diffraction by perfect crystal has been obtained and compared with the corresponding one based on the solution of the conventional Takagi–Taupin equations, $$\alpha =1.$$ In turn, notice that the value of order $$\alpha $$ may be adjusted from the experimental X-ray diffraction data.

Observation of deterministic double dissipative-Kerr-soliton generation with avoided mode crossing

Dissipative Kerr solitons (DKSs) in microresonators have boosted the development of the chip-scale ultrastable microcomb sources, and thrived in both fundamental physics and a wide range of applications. Among various DKS states, single DKS, double DKS, and a perfect soliton crystal could be identified simply based on the optical spectrum. Especially, the double DKS state, due to its two-pulse-interference nature, has recently found its own application in microwave photonics, such as reconfigurable rf filters. However, the traditional method to generate double DKS usually yields stochastically relative positions of the DKS in the cavity, which limits the versatility of the application. Here a method to deterministically generate double DKSs with fixed relative positions assisted by the dual-pump driven scheme in a 97-GHz ${\mathrm{Si}}_{3}{\mathrm{N}}_{4}$ microresonator is demonstrated. Via the dual-pump scheme, not only has the single soliton been repeatably generated, double DKS with deterministic relative positions has also been realized through backward tuning. The effects of pump wavelength tuning and pump power on the relative positions are investigated. A direct bridge between the relative positions and the avoided mode crossing induced modulated cw background is established. This work not only provides insight to DKS dynamics in a dual-pump scheme, but also improves the versatility of double-DKS based applications in microwave photonics.

Impact of solute-vacancy complex defects on ideal shear strength, stacking fault energy and elastic constants of perfect Ni crystals

Impact of solute-vacancy complex defects on ideal shear strength, stacking fault energy and elastic constants of perfect Ni crystals

Shock-induced energy localization and reaction growth considering chemical-inclusions effects for crystalline explosives

Chemical inclusions significantly alter shock responses of crystalline explosives in macroscale gap experiments but their microscale dynamics origin remains unclear. Herein shock-induced energy localization, overall physical responses, and reactions in α-1,3,5-trinitro-1,3,5-triazinane (α-RDX) crystal entrained various chemical inclusions were investigated by the multi-scale shock technique implemented in the reactive molecular dynamics method. Results indicated that energy localization and shock reaction were affected by the intrinsic factors within chemical inclusions, i.e., phase states, chemical compositions, and concentrations. The atomic origin of chemical-inclusions effects on energy localization is dependent on the dynamics mechanism of interfacial molecules with free space volume, which includes homogeneous intermolecular compression, interfacial impact and shear, and void collapse and jet. As introducing various chemical inclusions, the initiation of those dynamics mechanisms triggers diverse decay rates of bulk RDX molecules and hereby impacts on growth speeds of final reactions. Adding chemical inclusions can reduce the effectiveness of the void during the shock impacting. Under the shockwave velocity of 9 km/s, the parent RDX decay rate in RDX entrained amorphous carbon decreases the most and is about one fourth of that in RDX with a vacuum void, and solid HMX and TATB inclusions are more reactive than amorphous carbon but less reactive than dry air or acetone inclusions. The less-dense shocking system denotes the greater increases in local temperature and stress, the faster energy liberation, and the earlier final reaction into equilibrium, revealing more pronounced responses to the present intense shockwave. The quantitative models associated with the relative system density (RDsys) were proposed for indicating energy-localization mechanisms and evaluating initiation safety in the shocked crystalline explosive. RDsys is defined by the density ratio of defective RDX to perfect crystal after dynamics relaxation and reveals the global density characteristic in shocked systems filled with chemical inclusions. When RDsys is below 0.9, local hydrodynamic jet initiated by void collapse dominates upon energy localization instead of interfacial impact. This study sheds light on novel insights for understanding the shock chemistry and physical-based atomic origin in crystalline explosives considering chemical-inclusions effects.

Memory Effects in the Quiescent Crystallization of Polyamide 12: Self-Seeding, Post-Condensation, Disentangling, and Self-Nucleation beyond the Equilibrium Melting Temperature

This paper addresses the role of memory effects from earlier thermal protocols on the non-isothermal crystallization behavior of polyamide 12 (PA12). It turns out that memory effects can induce differences in crystallization temperatures as large as 30 °C when cooled from the melt at 10 °C/min. DSC experiments reveal that memory effects in PA12 result from (1) self-nucleation by the action of crystalline residues (self-seeding), (2) chemical post-condensation, and (3) polymer chain disentangling and re-entangling. Self-nucleation and disentangling facilitate crystallization, while melt post-condensation and re-entangling hamper it. It was demonstrated that repeated crystallization stimulates disentangling and that re-entangling in the liquid state proceeds more rapidly the higher the temperature. Effects due to solid-state post-condensation are very intriguing and particularly relevant to laser sintering based additive manufacturing. It was observed that solid-state post-condensation at 175 °C for 1 h negatively affects crystallization in a subsequent heating/cooling cycle but that solid-state annealing at 175 °C for 20 h leads to an enhanced crystal perfection and chain rearrangements whose non-crystalline self-nucleating remnants in the melt at 240 °C need more than 1 h to relax and no longer stimulate crystallization during cooling. Importantly, 240 °C is higher than the equilibrium melting temperature of PA12.

Unraveling the effect of excessive Al on the growth of high-quality YbAl3 film

Heavy-fermion YbAl3 intermetallic compound has attracted attention due to the distinctive 4f electronic structure and excellent electrical transport properties. However, it is extremely difficult to prepare high-quality YbAl3 film due to the highly saturated vapor pressure of Yb. Herein, the excessive Al strategy has been developed to grow high-quality YbAl3 films during both vacuum evaporating and annealing processes. The crucial role of excessive Al in growing YbAl3 film is revealed by the experimental and theoretical results. It is found that the excessive Al can effectively suppress Yb and Al vacancies and promote the crystallization of YbAl3 perfect crystal. The electrical conductivity and power factor of the as-prepared YbAl3 film can reach 1.71 × 106 S m−1 and 5.37 mW m−1 K−2, respectively. Our work demonstrates that keeping excessive Al is essential for the formation of high-quality YbAl3 films during the evaporating and annealing processes.

Growth and characterization of optical and thermal properties of LiGdF4 single crystal

The opportunity of growing of several centimeters in length LiGdF4 single crystals by Bridgman–Stockbarger technique was demonstrated and the optically perfect LiGdF4 single crystals with 8 mm and 55 mm in length were grown. The phase composition, thermal conductivity, basic optical and spectral-kinetic properties of LiGdF4 single crystals were studied for the first time. For LiGdF4 crystal, the resulting linear thermal expansion coefficients α is 11% larger, than for both LiYF4 and LiYbF4 crystals. The obtained thermal conductivity dependence k(T) is more pronounced compared to LiLuF4 and LiYF4. The absorption spectrum of the LiGdF4 crystal shows absorption bands corresponding to the 8S7/2 – (6Dj, 6Ij, and 6Pj) transitions of Gd3+ ions. The measured room temperature lifetime of 6Pj multiplet of Gd3+ ions was equal to 4.25 ± 0.05 ms. The values of the temperature gradient of the LiGdF4 refractive index do not strongly depend on the wavelength.