Bridgman Technique Research Articles

Single crystal growth by the Bridgman-Stockbarger technique of CaF2-rich - TmF3 solid solutions: Evidence of mixed valence Tm2+ and Tm3+ cations

Crystal growth and numerical simulation of CaF2-rich-based solid solution with TmF3 have been performed by the Bridgman-Stockbarger technique with initial Tm content 0.1 mol%, 1 mol% and 5 mol%. Centimeter-sized single crystals were obtained. Growth in the vicinity of (110) and (210) crystallographic directions have been identified as the natural crystal habit for the CaF2-rich- TmF3 solid solution with an axial thermal gradient about G=12 K.cm−1 and a pulling rate of v=4 mm.h−1. Optical absorption spectroscopy evidenced the presence of both Tm2+ and Tm3+ cations within the matrix. Their respective effective partition coefficients keff(Tm2+) and keff(Tm3+), close to unity, have been calculated. For low TmF3 initial content, with 0.1 mol.% and 1 mol.%, keff(Tm2+) >1 and keff(Tm3+) >1 whereas keff(Tm2+) <1 and keff(Tm3+) <1 for the attempt with 5 mol% TmF3 initial content. For this latter, a global effective partition coefficient, including both Tm3+ and Tm2+ contents, is logically deduced to be keff([Tm])<1. Chemical analysis carried out by ICP-AES and LIBS confirmed this trend with an effective partition coefficient of the global [Tm] content in the crystal that can be lower than 1. The global estimated partition coefficient of [Tm] in CaF2 matrix is thus ranging in between 0.906 and below 1 for 5 mol.% TmF3 molar fraction. The expected congruent melting point in the CaF2-rich-region of the CaF2-TmF3 phase diagram is evidenced and is higher than 1 mol.% and below 5 mol.% TmF3 molar fraction. Finally, carbon environment and TmF3 synproportionation reaction are pointed out as the main likely causes of Tm3+ cation reduction into Tm2+ during the growth process.

Spectroscopic study and visible luminescence of Tb3+ ions in CaF2 crystal co-activated with Yb3+

High quality crystals with composition of Ca0.95Tb0.05F2.05 and Ca0.85Tb0.05Yb0.1F2.15 were grown by Bridgman-Stockbarger technique. Yb3+ ions were used as a sensitizer for Tb3+ ions. Optical properties were measured, including the absorption spectrum, emission spectrum, and fluorescence decay curves. Judd-Ofelt theory was used to analyze the spectroscopic parameters. Fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency were determined. The emission cross section of Tb3+ ions in Tb:CaF2 and Tb/Yb:CaF2 crystals for the green emission at 544 nm, corresponding to the transitions of 5D4→7F5 were calculated to be 4.61x10-22 cm2 and 4.60x10-22 cm2, respectively. Our experiments have shown that doping with Yb3+ ions does not significantly affect the spectral properties of Tb3+ ions in CaF2 crystal. Quadratic dependence of the emission intensity of Tb3+ ion in Tb/Yb:CaF2 crystal on the intensity of a diode laser at 955 nm proved that the excitation of Tb3+ ion occurs due to the cooperative process of transferring the excitation from two Yb3+ ions to one neighboring Tb3+ ion. The Tb/Yb:CaF2 crystal can be considered as a promising up-converting medium for creating diode-pumped visible phosphorus and active laser media.

Photophysical properties of [formula omitted] crystals: Photoconductivity and photoluminescence studies

The Ga0.95B0.05Se compound was synthesized through the direct melting of constituent elements in stoichiometric proportions, followed by the growth of a single crystal using the horizontal Bridgman technique. Within the temperature range of 300–400 K, the activation energies of charge carriers in the crystal were determined to be 1.81 eV in darkness and 1.538 eV under illumination. Two acceptor levels were identified at 0.703 eV and 0.28 eV above the valence band. Notably, under conditions of intense optical excitation, the recombination of nonequilibrium charge carriers exhibited a decay time of 12 ns. This rapid recombination process suggests that the material is highly suitable for use in photodetectors capable of converting optical signals into electrical signals, leveraging its fast response time.

Sustained hydrogen production through alkaline water electrolysis using Bridgman–Stockbarger derived indium-impregnated copper chromium selenospinel

The depletion of conventional fossil fuels necessitates the development of sustainable energy alternatives, with electrochemical water splitting for hydrogen (H2) production being a promising solution. However, large-scale hydrogen generation is hindered by the scarcity of cost-effective electrocatalysts to replace noble metals such as Pt and RuO2 in the Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). In this study, we report the synthesis of CuCr2-xInxSe4 (x = 0, 0.2, 0.4) using a dual approach combining the Bridgman-Stockbarger method and ball milling. Among the synthesized materials, CuCr1.8In0.2Se4 demonstrates outstanding HER activity in 1.0 M KOH, achieving a potential of −0.16 V vs. RHE at a current density of 10 mA cm−2. Moreover, the material shows remarkable durability during a three-electrode accelerated degradation test in an alkaline medium, maintaining its performance over 24 h at a constant current density of −200 mA cm−2, with a stable potential of −0.57 V vs. RHE. Additionally, CuCr1.8In0.2Se4 was tested in a two-electrode configuration alongside CoFe LDH, achieving a benchmark of 1.7 V for overall water splitting. It sustained a current density of 400 mA cm−2 for 24 h in an accelerated degradation test, exhibiting a minimal loss of 0.1 V after the testing period. These results highlight CuCr1.8In0.2Se4 as a promising non-noble metal catalyst for HER, demonstrating its potential to reduce reliance on noble materials for large-scale hydrogen production.

Mixed-valence Sm-doped LaF3 crystals as ion-electron conductors: Crystal growth and impedance characterization

The single crystals with the composition La1−y(Sm3+1−xSm2+x)yF3−xy (y = 0.04) were grown from melt by the vertical Bridgman technique. A part of the Sm3+ doping ions in LaF3 matrix is reduced to the Sm2+ oxidation state due to interaction with carbon during the growth process. The crystals were studied by X-ray diffraction analysis, optical and impedance spectroscopy. The Sm-doped crystals LaF3 are single-phase, retaining the tysonite-type structure (sp. gr. P3̄c1) and demonstrate a bipolar electrical conductivity mechanism. Both the ionic conductivity σi = 4.7 × 10−5 S/cm caused by heterovalent substitutions of La3+ for Sm2+ and the comparable electronic conductivity σe = 3 × 10−5 S/cm due to the variable oxidation states Sm2+/Sm3+ ions were detected for the grown crystals. The discovered mixed ionic-electronic conductivity of La0.96Sm3+0.004Sm2+0.036F2.964 crystals opens up a new direction for the practical application of the tysonite-type fluorides as a component of electrode materials for fluorine-ion current sources.

Growth and optical properties of high-concentration Ho3+ ion-doped Ba(Y1−xLux)2F8 crystal for mid-infrared laser application

30mol% Ho:BaY2F8 (Ho:BYF) and 30mol% Ho, 20mol% Lu:BaY2F8 (Ho:BYLF) crystals with monoclinic phase were prepared by the Bridgman technique. After introducing Lu3+ ions, the thermal property of Ho:BYLF crystal was improved without significantly shortening the 5I5 level lifetime of Ho3+ ion compared with Ho:BYF crystal. Under laser diode pumping at 889 nm, the emission peaks of both Ho:BYF and Ho:BYLF crystals in the range of 3–5 μm could be detected. The spectral parameters of the crystal are calculated in detail, and the cross sections of absorption, emission and gain are given. During laser pumping, the two crystals showed low pumping threshold, and Ho:BYF crystal obtained a maximum energy output of 5.22 mJ, while Ho:BYLF crystal tended to be saturated at 1 mJ due to the high concentration of Lu3+ ion. These two crystals show great application potential for laser operating in the mid-infrared range.

Investigation of Sm[formula omitted] as a near-infrared emitting activator for NaI scintillators

NaI is the most commonly used host lattice for scintillators, which makes it interesting to further improve its scintillation properties. Many alternative activators have been tried instead of the conventionally used Tl+. In this work, Sm2+ is used as an near-infrared emitting activator for NaI to study whether it is suitable for readout with silicon based photodetectors. NaI single crystals (co-)doped with 0-0.2% Tl+ and 0.2%–2% Sm2+ were grown by the vertical Bridgman technique. The emission of the samples was studied under optical and X-ray excitation. It is shown by photoluminescence decay studies that Tl+ works as a sensitiser for Sm2+. The samples indicate the formation of multiple (at least 5) different Sm2+ emission sites. Annealing the samples changes their emission intensity and scintillation properties. NaI:Sm2+ shows great similarities with its Eu2+-doped counterpart. Finally, it is demonstrated that NaI:Sm2+ can be read out with silicon photomultipliers and an energy resolution of 11% has been attained.

Synthesis and properties of quasi-one-dimensional BiSBr crystals via the Bridgman-Stockbarger technique

This investigation details the synthesis and comprehensive characterization of semiconducting bismuth sulfobromide (BiSBr) crystals, emphasizing their structural and optoelectronic properties. Using the Bridgman-Stockbarger technique, we synthesized large, high-quality BiSBr crystals, which were systematically examined through techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. These methods confirmed the crystals’ quasi-one-dimensional structure and their exceptional stability, demonstrating an absence of surface oxidation, which is a significant advantage for optoelectronic applications. The study establishes a correlation between the crystals’ unique structural characteristics and their enhanced optoelectronic properties, particularly regarding light absorption and thermal conductivity, thereby underscoring their potential in sustainable energy technologies. This work not only advances our understanding of BiSBr as a promising material for optoelectronic devices, but also paves the way for future research into its practical applications in energy conversion and storage systems.

Fabrication and Evaluation of Spectroscopic Grade Quasi-hemispherical CdZnTe Detector

Background: This study focuses on the fabrication and characterization of quasi-hemispherical Cd&lt;sub&gt;0.9&lt;/sub&gt;Zn&lt;sub&gt;0.1&lt;/sub&gt;Te (CZT) detector for gamma-ray spectroscopy applications, aiming to contribute to advancements in radiation measurement and research.Materials and Methods: A CZT ingot was grown using the vertical Bridgman technique, followed by proper fabrication processes including wafering, polishing, chemical etching, electrode deposition, and passivation. Response properties were evaluated under various external bias voltages using gamma-ray sources such as Co-57, Ba-133, and Cs-137.Results and Discussion: The fabricated quasi-hemispherical CZT detector demonstrated sufficient response properties across a wide range of gamma-ray energies, with sufficient energy resolution and peak distinguishability. Higher external bias voltages led to improved performance in terms of energy resolution and peak shape. However, further improvements in defect properties are necessary to enhance detector performance under low bias conditions.Conclusion: This study underscores the efficacy of quasi-hemispherical CZT detector for gamma- ray spectroscopy, providing valuable insights for enhancing their capabilities in radiation research field.

Modified Bridgman assisted ZnTe crystal growth for THz device applications

Zinc Telluride (ZnTe) single crystals have enormous potential for generating and detecting broadband terahertz (THz) radiation, making them suitable for a wide range of applications in communication, defence security and biomedical applications. The quality and homogeneities of the crystal plays an important role in obtaining THz response. This paper elaborates on the steps involved in the crystal growth of ZnTe and the characterization technique utilized for the determination of quality of the grown crystal, identifications of defects and qualifications of THz signals. Single crystal was grown by the Bridgman technique in vacuum sealed carbon-coated quartz ampoule with excess tellurium (Zn:Te/3:7). To obtain maximum THz response, crystals were oriented along (110) direction using a Laue diffraction pattern and sliced accordingly. Three different crystals along the length (bottom-middle-top) of size ∼ 10 mm × 10 mm are taken for analysis. The crystallinity of ZnTe was confirmed with X-ray diffraction pattern and lattice parameters were obtained using Rietveld refinement. Raman analysis was carried out at three different regions of the grown crystal which revealed the presence of same high-intensity mode at 413 cm−1 in all the regions confirming the quality of the crystal. The EDS compositional analysis confirms the stoichiometry along the grown crystal length. Optical bandgap of 2.216 eV was measured by UV-Vis-NIR spectra and >55 % transmission was obtained across the grown crystal length. The size and distribution of Te inclusions were measured using IR microscopy. The crystals were subjected to terahertz investigation in the range of 0.1–4 THz using a time domain spectrometer. All the crystals exhibited negligible absorption coefficients in the 0.1–3.75 THz range, confirming the maximum transmission in the THz domain. The crystals also exhibit excellent electro-optic detection which is confirmed by signal-to-noise ratio in the measured range.

High sensitivity dual-mode ratiometric optical thermometry based on Ce3+/Mn2+ co-doped LiYF4 single crystal

Serial dual-emitting single crystals LiYF4: 0.5Ce3+/αMn2+ (α = 0, 0.05, 0.1, 0.3, 0.5, and 1.0) samples were synthesized by a reformative Bridgman technique. A comprehensive investigation was carried out to systematically analyze the crystal structure, energy transfer mechanism, luminescence properties, and temperature-dependent sensing capabilities. The single crystal exhibits distinct dual broadband emissions, with peaks at 373 nm attributed to the transition from 5d to 4f of Ce3+ ions and 555 nm assigned to the transition from 4T1g(4G) to 6A1g(4S) level of Mn2+ ions. The optical properties of the Ce3+/Mn2+ co-doped LiYF4 single crystal were studied in relation to temperature, with a focus on enabling precise optical temperature measurements. The research revealed a relative sensitivity of 0.995 % K−1 at 498 K and temperature resolution of 0.03 K at 498 K, indicating the potential of LiYF4: Ce3+/Mn2+ single crystals for use in highly sensitive optical thermometry applications. These findings highlight the crystal suitability for the development of temperature sensing devices with enhanced sensitivity and resolution.

Effect of stacking fault energy (SFE) of single crystal, equiatomic CrCoNi and Cantor alloy on creep resistance

Compared to mechanisms like solid solution strengthening, the stacking fault energy (SFE) should be considered as a further factor that influences the material properties. The effect of SFE of alloys or individual elements on strength and resistance can vary considerably. In the high-temperature regime above 700 °C, there are still significant gaps in the knowledge about the effect of the SFE on the mechanical properties of single-phase alloys. The effect of SFE on creep resistance of two face-entered cubic equiatomic medium and high entropy alloys, CrCoNi and CrMnFeCoNi, respectively, is evaluated to fill parts of these gaps. Using the Bridgman solidification process, the alloys were produced as single crystals and crept under vacuum at 700 °C up to 1100 °C. This work shows a significant impact of the lower SFE of CrCoNi on the creep behavior compared to the results of previous investigations of CrMnFeCoNi. The creep resistance of the former is higher over the complete temperature range. At very high temperatures, the strengthening effect of the stacking faults is significantly present. The formation of tetragonal stacking faults and extended dislocation nodes can be identified as the reason for this effect.

Impact of doping on the Bridgman grown organic stilbene single crystal for third order NLO applications

Transparent 1, 3, 5-Triphenylbenzene doped Stilbene (TBS) single crystal was successfully grown by employing the Bridgman technique. SCXRD studies found crystallographic parameters, which reveal that the TBS single crystal has crystallized in a monoclinic crystal structure with the space group of P21/C. The identification of the functional groups in the TBS crystal was accomplished through the FTIR analysis. The UV–Vis spectral data shows that the TBS crystal exhibits minimal absorption across the visible spectrum, with a lower cutoff wavelength of 365 nm. The violet emission is observed at 380 and 405 nm in the fluorescence analysis. Additionally, the crystal's high quality was confirmed by a full width at half maximum value of 123 arcsec in the prominent rocking curve peak. Third-order nonlinear optical susceptibility χ(3) was determined to be 4.26 × 10−6 esu using the Z-scan technique. These are exciting findings that highlight the TBS crystal's suitability for various applications, including scintillation and optoelectronic device fabrication.

Experimental Simulation of Directional Crystallization of SiMo Cast Iron Alloyed with Al and Cr.

SiMo ductile cast iron combines ease of part fabrication with good mechanical properties, including a usable plasticity range. Its poor corrosion resistance inherited from grey cast iron could be alleviated through alloying with Al or Cr additions capable of forming a dense oxide scale protecting the substrate. However, the presence of Al and Cr in cast iron tends to make the material brittle, and their optimum alloying additions need to be studied further. The present work was aimed at investigating the effect of crystallization rates on microstructure changes during directional crystallization of SiMo-type alloys with up to 3.5% Al and 2.4% Cr. The experiment was performed using the Bridgman-Stockbarger method. The tubular crucible was transferred from the hot section to cold section at rates ranging from 5 mm/h to 30 mm/h with a 4/5 crucible length and then quenched. The introduced Al promoted graphitization up to a point, wherein, at the highest applied addition, the graphite precipitation preceded crystallization of the rest of the melt. A rising level of Cr in these alloys from 1% to 2.4% resulted in the formation of low and high contents of pearlite, respectively. The higher crystallization rates proved effective in increasing the ferrite content at the expense of pearlite. In the investigated cast iron samples with smaller applied alloying additions, Widmanstätten ferrite or ausferrite, i.e., fine acircular phase, were often found. The switch from directional crystallization to quenching caused a transition from a liquid to solid state, which started with nucleation of islands of fine austenite dendrites with chunky graphite eutectic separating them. As these islands expanded, they pushed alloying additions to their sides, promoting carbide or pearlite formation in these places and forming a super-cell-like structure. The performed experiments helped gather information concerning the sensitivity of the microstructure of SiMo cast iron modified with Al and Cr to crystallization rates prevailing in heavy cast structures.

Study on scintillation properties and proton-induced radiation damage of LaCl[formula omitted] crystals

A Cs2LiYCl6 (CLYC) scintillation crystal is a promising candidate for fast neutron spectroscopy due to its dual mode gamma/neutron capability and good energy resolution. Despite promising features, CLYC’s limited radiation tolerance and inability to separate alpha/proton particles using pulse shape discrimination (PSD) method restrict its applicability in fast neutron spectroscopy. The significant cross-sections for 35Cl(n,p)35S and 35Cl(n, α)32P reactions make 35Cl-containing crystals attractive candidates for fast neutron detection, prompting their development as a promising new solution. This study reports the growth of LaCl3 crystals via the Bridgman technique, enabling further exploration of their scintillation and material properties for fast neutron detection applications. The effects of the proton irradiation on LaCl3 crystals were investigated by irradiating them with a 100 MeV proton beam at the Korea Multi-purpose Accelerator Complex. The study quantified radiation damage by comparing the pre- and post-irradiation scintillation properties and PSD of the LaCl3 crystals. The results of the measurements demonstrate that LaCl3 crystals are promising candidates for applications in fast neutron identification, spectroscopy, and space mission, maintaining performance even under high-radiation environments.

Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method

PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method.

The effect of Fe content on the dielectric properties of TlGa(0,999)Fe(0,001)S2 thin films

0,1 % iron containing Thallium Gallium Sulfide (TlGaS2 and TlGa(0,999)Fe(0,001)S2) thin films were deposited by thermal evaporation in the thickness range 20–200 nm. Raw bulk TlGaS2 and TlGa(0,999)Fe(0,001)S2 crystals were produced using the Bridgman technique. Iron (Fe) content was free, and the bonding content of a polarized charged group in the crystal and thin films was detected in the X-ray diffraction patterns. The dielectric characteristics of the thin films were determined by dielectric spectroscopy. The dielectric results showed Fe content polarizing in space-charge characteristics in the 1–100 Hz frequency range. Besides, the position and magnitude of dipolar polarization supported the presence of dipolar polarized charged groups having Fe content. In addition, it was realized that the void density explicitly affects the dielectric constant. The void density decreased toward higher thicknesses, whereas the dielectric constant increased. The ac conductivity results contributed to evaluating the effect of thickness for each thin film. The overall analysis indicated that even a small percentage of Fe (0,1 %) has a remarkable impact on the dielectric properties and electrical conduction of TlGa(0,999)Fe(0,001)S2 thin films. This analysis can provide opportunities to improve the electrical abilities of Thallium Gallium Sulfide (TlGaS2) thin films, which have applications as receivers of visible and infrared emission, X-ray and gamma-ray detectors, neutron detectors, barometers, and piezoelectric photoresistors if the presence of Fe is considered as investigated in TlGa1−xFexS2 thin films.

Stacking fault energy, thermal expansion behavior, and elastic coefficients of a single-crystalline CrFeNi medium-entropy alloy

The equiatomic CrFeNi alloy is considered to be a model single-phase face-centered cubic medium-entropy alloy. The Bridgman technique was employed to grow a single crystal of this alloy and its dilatation behavior and elastic properties were measured in the temperature range: 100 K–673 K. Based on transmission electron microscopy investigations, plastic deformation is initially caused by the glide of dissociated dislocations (Shockley pairs bounded by a stacking fault ribbon). From their dissociated widths, a stacking fault energy of 36 mJ∙m-2 was determined.

Improving Microstructural Homogeneity of Investment‐Cast Single‐Crystalline Ni‐Base Superalloys by Using Fluidized Carbon Bed Cooling

One impeding factor for faster solidification in typical investment casting processes is the limited heat removal capability. This study compares the classical Bridgman technique and the fluidized carbon bed cooling (FCBC) casting method. In particular, the influence of the thermal design is investigated in terms of microstructural and compositional homogeneity in single‐crystalline CMSX‐4. These investment casting processes mainly differ in the baffle type used to insulate the hot and cold zones inside of the casting vessel. While the Bridgman process is based on radiation cooling, the FCBC casting process relies on a dynamic baffle made of expanded graphite that is buoyant on fluidized bed of glassy carbon beads. Such a dynamic insulation layer can adapt to the cross‐sectional variation of ceramic shell molds and provide a better thermal insulation, which results in more uniform solidification conditions. This enables a reduction in the primary dendrite arm spacing by up to 26%, an increase in the homogeneity of the microstructure and composition, as well as a reduction in overall porosity and mean pore size of 41%.

Rapid formation of imidazolium glutarate (IMGA) compound and investigation of its single crystal growth by modified vertical Bridgman technique for optical limiting applications

In this paper, we have examined the formation of the imidazole glutarate adduct by protonation-deprotonation between imidazole and glutaric acid using a direct precipitation method within a short period. Following that, we have succeeded in growing imidazolium glutarate (IMGA) single crystaldirectly from synthesized material and we have also grown IMGA single crystal from the melt methodusing the vertical Bridgman technique for the first time in literature. A special Bridgman furnace was constructed with a slight modification in the winding section for this crystal growth. Crystal structure, phase purity, and growth plane were analyzed for the grown crystal from both single and powder XRD analysis. Functional groups were verified after the growth using FTIR transmittance analysis. The optical homogeneity and growth mechanism were scrutinized by birefringence interferogram and chemical etching studies, respectively. The grown IMGA has 80 % transparency in the entire visible region. The cut-off wavelength of the grown crystal is 235 nm, and the optical band gap energy of IMGA was found to be 5.26 eV. The photocurrent study reveals that IMGA has a negative photoconductivity nature. Third-order nonlinear parameters were found by the Z-scan technique. IMGA has a self-defocusing nature, negative non-linearity, and saturated absorption properties. The calculated χ(3) value is 2.045 x 10-8 esu.