Bridgman Technique Research Articles

Yb3+, Er3+: CeF3 crystals: Growth, first-principles simulation, and near-infrared optical properties

Yb3+, Er3+: CeF3 crystals were successfully grown via Bridgman-Stockbarger technique, and their structure and physicochemical properties were characterized and analyzed. The results have shown that the maximum phonon vibrational frequency of the crystals is 391 cm−1. Under 980 nm excitation, Yb3+ ions doping can effectively improve the luminescence intensity at 1550 nm. The maximum luminescence intensity was achieved at the Yb3+ ion concentration of 3 at.%. The energy transfers, concentration quenching mechanisms and the factors affecting the fluorescence decay time were investigated in detail. The band gap structure, density of states and charge distribution of Yb3+, Er3+: CeF3 crystals were studied in depth by first principles simulation. This work proves that Yb3+, Er3+: CeF3 crystals have great potential for the near-infrared laser applications.

Scintillation property of undoped NaI transparent ceramics

In this study, NaI transparent ceramics were synthesized by the spark plasma sintering method, also optical and scintillation properties were investigated. To evaluate the potential of the transparent ceramics, a NaI single crystal was also prepared by the vertical Bridgman–Stockbarger method. The diffuse transmittance of the transparent ceramic fabricated at 470 °C was equivalent to that of the single crystal. All the samples showed scintillation peaking at 320 nm due to self-trapped exciton. In addition, scintillation peaks ascribed from lattice defects were detected at 450 nm for the transparent ceramics and 540 nm for the single crystal. The scintillation decay time constants of the transparent ceramic fabricated at 440 °C were 5.7, 18, and 189 ns. The light yield of the transparent ceramic turned out to be 910 photons MeV−1 and was two-thirds of the single crystal.

The relationship between ionic conductivity and structural characteristics of melt-grown KR 3F10 (R = Tb, Dy, Ho, Y) single crystals

Abstract The temperature dependences of the ionic electrical conductivity of fluorite-type (sp. gr. F m 3 ‾ m $Fm\overline{3}m$ , Z = 8) KDy3F10 and KHo3F10 single crystals grown by the Bridgman technique have been studied by impedance spectroscopy for the first time. The correlation between the conductometric and structural characteristics of KR 3F10 (R = Tb, Dy, Ho, Y) crystal family from the point of view of the observed size effect in the ionic conductivity is discussed. With decrease in the unit-cell volume V 1F per fluorine atom in a series of crystals with R = Tb, Dy, Ho and Y, the activation energy Eσ of ion transfer decreases from 1.57 to 1.16 eV respectively and the fluorine-ion conductivity value increases from 3.0 × 10−5 to 4.4 × 10−4 S cm at 773 K, i.e. the nature of the conductivity change is linearly antibatic. This phenomenon can be useful for developing approaches and search strategies for new ionic conductors.

Growth, optical and thermal properties of triphenylamine single crystal grown by modified Vertical Bridgman method for optical application

Triphenylamine single crystal was grown by the modified low-temperature vertical Bridgman technique. Physical, structural, and optical properties such as thermal stability, transmittance, crystalline nature, and crystalline perfection of the triphenylamine crystal were investigated. The orientation of the grown crystal was analyzed by PXRD analysis. It reveals that the grown crystal has (043) plane direction. The crystal perfection was studied through HRXRD analysis and it is found that full-width half maximum of the grown TPA crystal is 70 arc-sec. Thermal stability, melting, and freezing points of the grown crystal are analyzed by thermogravimetric and differential thermal analyses. The UV–Vis–NIR analysis was used to determine the optical transparency and cut-off wavelength value of the TPA crystal. The optical parameters such as bandgap, reflectance, refractive index, and Urbach energy have been calculated using UV–Visible analysis. The maximum emission peak of the TPA crystal was observed at 379 nm through Fluorescence Analysis. The obtained crystal's nonlinear optical property (SHG efficiency) has been evaluated by utilizing the Kurtz and Perry powder second harmonic method. The result reveals that the grown TPA crystal is suitable for non-linear optical applications.

Anisotropic Thermal Expansion and Electronic Structure of LiInSe2.

Optical quality cm-sized LiInSe2 crystals were grown using the Bridgman–Stockbarger method, starting from pure element reagents, under the conditions of a low temperature gradient of 5–6 degrees/cm and a slight melt overheating. The phase purity of the grown crystal was verified by the powder XRD analysis. The thermophysical characteristics of LiInSe2 were determined by the XRD measurements in the temperature range of 303–703 K and strong anisotropy of the thermal expansion coefficients was established. The following values of thermal expansion coefficients were determined in LiInSe2: αa = 8.1 (1), αb = 16.1 (2) and αc = 5.64 (6) MK−1. The electronic structure of LiInSe2 was measured by X-ray photoelectron spectroscopy. The band structure of LiInSe2 was calculated by ab initio methods.

A Quintuple-Layered Binary Chalcogenide Sb2Te3 Single Crystal and Its Transport Properties for Thermoelectric Applications.

The binary chalcogenide material Sb2Te3 was synthesized via the melting technique. The synthesized materials were converted to a single crystal through the Bridgman–Stockbarger technique. The phase purity and structural properties of the grown crystal were analyzed using powder X-ray diffraction and single-crystal X-ray diffraction measurements. X-ray photoemission spectroscopy reveals the local intermolecular bonding, changes in the stoichiometry, and the oxidation states of the elements present in the crystal. Transport properties like electrical resistivity, Seebeck coefficient, and thermal conductivity were measured. The power factor and figure of merit (ZT) of the grown crystal were calculated.

Orientation Control for Nickel-Based Single Crystal Superalloys: Grain Selection Method Assisted by Directional Columnar Grains.

The service performance of single crystal blades depends on the crystal orientation. A grain selection method assisted by directional columnar grains is studied to control the crystal orientation of Ni-based single crystal superalloys. The samples were produced by the Bridgman technique at withdrawal rates of 100 μm/s. During directional solidification, the directional columnar grains are partially melted, and a number of stray grains are formed in the transition zone just above the melt-back interface. The grain selected by this method was one that grew epitaxially along the un-melted directional columnar grains. Finally, the mechanism of selection grain and application prospect of this grain selection method assisted by directional columnar grains is discussed.

Growth and characterization of detector-grade CdMnTeSe

The Cd0.95Mn0.05Te0.98Se0.02 (CMTS) ingot was grown by the vertical Bridgman technique at low pressure. All wafers showed high resistivity, which suggests potential as a room-temperature semiconductor detector. The resistivity of the CMTS planar detector was 1.47 × 1010 Ω· cm and mobility lifetime product of electrons was 1.29 × 10−3 cm2/V. The spectroscopic property with Am-241 and Co-57 was evaluated. The energy resolution about 59.5 keV gamma-ray of Am-241 was 11% and the photo-peak of 122 keV gamma-ray from Co-57 was clearly distinguished. The result shows the first detector-grade CMTS in the world and proves CMTS’s potential as a radiation detector operating at room temperature.

Intense 2.9 µm mid-infrared emission from Dy3+/Yb3+：SrF2 crystal under 975 nm excitation

The intense 2.9 µm MIR (mid-infrared) luminescence corresponding to the Dy 3+ : 6 H 13/2 → 6 H 15/2 transition was achieved for the first time in Dy 3+ /Yb 3+ ions co-doped SrF 2 crystals. 2 at% Dy 3+ : SrF 2 ，2 at% Dy 3+ /5 at% Yb 3+ : SrF 2 , and 5 at% Yb 3+ : SrF 2 crystals were grown by Bridgman method. The influence of Yb 3+ on its spectral properties and energy transfer mechanisms has been studied. In comparison to Dy 3+ doped SrF 2 crystals, Dy 3+ /Yb 3+ co-doped crystals exhibit not only intense 2.9 µm emission but also longer high laser energy level lifetimes, favoring 2.9 µm population inversion and lasing behavior. Furthermore, the ET efficiency from Yb 3+ to Dy 3+ in Dy 3+ /Yb 3+ co-doped crystals is found to be as high as 95.34%, indicating that the ET from Yb 3+ is efficient. The results show that incorporating Yb 3+ into Dy 3+ : SrF 2 crystals improves the ability to achieve 2.9 µm lasing action, which could be used as a potential gain media for laser diode-pumped MIR lasers. • The Dy 3+ , Dy 3+ /Yb 3+ and Yb 3+ doped SrF 2 single crystals were grown by the Bridgman-Stockbarger method. • Intense 2.9 µm mid-infrared emission is observed in Dy 3+ /Yb 3+ : SrF 2 crystal under 975 nm excitation. • Detailed spectroscopic properties and energy transfer mechanisms were studied. • Dy 3+ / Yb 3+ : SrF 2 crystals are expected to achieve mid-infrared laser output.

Very high cycle fatigue durability of an additively manufactured single-crystal Ni-based superalloy

A single crystalline (SX) nickel-based superalloy additively manufactured (AM) by electron beam-based powder bed fusion (PBF-E) was investigated under very high cycle fatigue (VHCF) at 1,000 °C in fully reversed conditions (R ε = −1). Specimens processed using a classical Bridgman solidification route and the impact of a hot isostatic pressing (HIP) treatment were also considered. It is shown that the fatigue lifetime of the AM specimens is higher or in the same range of the Bridgman processed ones with the same chemical composition. All defect-free AM samples fail by surface initiation with very long VHCF lives. In the absence of metallurgical defects such as grain boundaries or pores, the superalloy chemical stability against oxidation governs VHCF failure. • Additively manufactured and Bridgman solidified CMSX-4 superalloy have comparable VHCF life under high temperature. • The superalloy chemistry controls the fatigue life of defect-free specimens. • Defect-free specimens fails by surface crack initiation. • The fatigue limit is controlled by the superalloy oxidation resistance at temperature of 1,000 °C.

Crystal growth, density functional theory, and scintillation properties of TlMgX3 (X = Cl, Br, I)

In this paper we report on the crystal growth, density functional theory (DFT) calculations and scintillation properties of TlMgX3 (X = Cl, Br, I). Crystals were grown by the Vertical Bridgman technique up to 16 mm in diameter and 25 mm long. Crystals of TlMgCl3 and TlMgBr3 belong to the family of the Perovskites and have the orthorhombic crystal structure. As a congruently melting composition, TlMgI3 does not exist but probably forms Tl2MgI4 instead.

Crystal growth and luminescence characterizations of halide scintillators K2LaBr5:Eu2+

Recent researches have shown that Eu2+ ion heterovalently doped rare earth halide scintillators attract the attention of researchers. In this paper, the transparent K2LaBr5 scintillation crystals of centimeter size doped with heterovalent Eu2+ were successfully grow by the vertical Bridgman technique. X-ray powder diffraction analysis shows that the crystal has an orthonormal structure with space group Pnma(62). A small amount of Eu2+ doping does not change the internal structure of the crystal.The transmittance, the UV–visible excited spectrum and emission spectrum, X-ray excited luminescence spectrum, Photoluminescence decay time and scintillation pulse decay time have been measured at room temperature. The results show that the crystal has strong luminescence intensity, and the maximum emission peak is about 430 nm. The photoluminescence decay time of K2LaBr5:xmol.%Eu2+(x = 0.5, 1, 2) are 5.56 μs, 5.67 μs and 7.03 μs, respectively. The decay time of K2LaBr5:Eu2+ crystal under 137Cs 662 keV radiation is nanosecond, indicating that the K2LaBr5:Eu2+ crystal has fast decay characteristics and excellent time resolution performance.

Growth of thallium-doped CsI/CsCl/KCl eutectics and their scintillation properties

In this study, Tl:CsI/CsCl/KCl ternary eutectic scintillators were grown using the vertical Bridgman–Stockbarger method by unidirectional solidification. The CsI and KCl phases were elongated along the growth direction, based on backscattered electron imaging (BEI) observations. The Tl:CsI scintillator phase grew as a matrix, which can be used to create optical waveguides for scintillation light. The expected Tl+ emission peak was observed at 550 nm under X-ray excitation. This emission was attributed to the self-trapped excitons perturbed by TI+ in Tl:CsI. The decay time of the Tl:CsI/CsCl/KCl eutectic was 285 ns, and its light output was estimated to be 10,800 photons/MeV.

Piezomodulation of electrical conductivity in TlIn0.9Ga0.1Se2 single crystals

In the present work, the piezoelectric properties of TlIn[Formula: see text]Ga[Formula: see text]Se2 single crystals are investigated. Single crystals were grown by the Bridgman–Stockbarger method. The results show that when periodic mechanical vibrations are excited in these crystals, the electrical conductivity is modulated at the same frequency. Measurements of the amplitude values of the piezoconductivity at the same degree of deformation in the dark and under different illumination revealed the presence of a linear relationship between them. The level of the piezosignal also changes linearly depending on the strength of the magnetic field. Thus, TlIn[Formula: see text]Ga[Formula: see text]Se2 crystals have a potential prospect of application in the field of highly sensitive magnetic and light sensors.

Fermi energy-level shift of p-type AgBiSe2 single crystal featuring semiconductor-to-metal transition at cryogenics

A ternary chalcogenide AgBiSe2 (ABS) crystal was grown using the Bridgman–Stockbarger technique followed by XRD and Raman shift analysis to verify the structural properties of the ABS crystal. The temperature (300–4.2 K)-dependent resistivity (ρ) shows semiconductor behavior down to 109 K and transforms to metallic behavior down to 19 K. Due to the localization behavior, the resistance shows an upturn up on further decrease in temperature. Charge defects caused by atomic vacancies as well as anti-site defects are thermodynamically induced, and have the potential to shift the Fermi energy level. The two transitions at 109 and 19 K in ρ(T) demonstrate consequent changes as a semiconductor-to-metal transition. The magnetoresistance MR graph exhibits resistive behavior with respect to the magnetic field applied and displays a ‘U’ shape at 300 K, which changes to a ‘V’ shape at 4.2 K. The Hall effect measurements reveal that the majority carrier is a hole. The carrier density as well as mobility changes with respect to temperature are analyzed within the preview of the Ioffe–Regel criterion. ABS is a promising p-type candidate with efficient characteristics that needs further elaboration for thermoelectric, photonic and photovoltaic applications.

The High-Energy Milling Preparation and Spectroscopic Characterization of Rare-Earth Ions Doped BaY2F8 Nanoparticles

BaY2F8 nanoparticles (NPs), doped with Yb3+ and Er3+ ions, were successfully produced by high-energy ball-milling. High-quality monoclinic single crystals (sp. gr. C2/m, a = 0.6969(3), b = 1.0502(1), c = 0.4254(1) nm, β = 99.676°) grown from the melt by the Bridgman technique were used as raw materials. The prepared nanocrystals were comprehensively studied by X-ray diffraction analysis, transmission electron microscopy, and optical spectroscopy. The fabrication possibility of single-phase irregular shaped Ba(Y0.964Yb0.030Er0.006)2F8 NPs in the size range of 20–100 nm with a milling duration of 10 h at 600 rpm is demonstrated. Ba(Y0.964Yb0.030Er0.006)2F8 NPs show intense luminescence by both up- (λ = 540 and 650 nm) and down-conversion (λ = 1540 nm) mechanisms upon IR excitation (λ = 980 nm). A qualitative comparison of the spectroscopic characteristics of the produced Ba(Y0.964Yb0.030Er0.006)2F8 NPs with the initial bulk crystal and the widely used up-conversion β-Na1.5(Y1.17Yb0.3Er0.03)F6 NPs is presented. Experimental data offer great opportunities of the Ba(Y0.964Yb0.030Er0.006)2F8 NPs applications in nanophotonics and biotechnology. High-energy ball-milling has potential as a versatile method for the scalable production of fluoride nanoparticles.

Pr3+:LiGdF4 microparticles for optical temperature sensing

Single crystal of Pr3+:LiGdF4 (CPr = 0.01 at.%) was grown in the resistive furnace by the Bridgman-Stockbarger method. The crystal was milled in an agate mortar. The obtained powder had a tetragonal structure (88 space group I41/a). The specific heat of the sample gradually increases with the increase of temperature from 0.46 (at 200 K) to 0.62 J/g·K (at 389 K). These values are notably less in comparison to the phosphors based on LiYF4 and LiLuF4 counterparts. The luminescence spectra of Pr3+:LiGdF4 microparticles under 442 nm pulse laser excitation demonstrated temperature dependence of its shape in the 80–680 K temperature range. Specifically, the intensity of 3P1 – 3Hj emission increases in reference to 3P0 – 3Hj emission with the increase of temperature. This phenomenon was explained by the fact that 3P1 and 3P0 electron levels share their electron populations according to the Boltzmann law. The luminescence intensity ratio (LIR) was taken as a temperature-dependent parameter. The maximal absolute temperature sensitivity (Sa) was equal to 0.010 K−1 at 320 K. This value is bigger in comparison to other Pr3+ doped counterparts.The high temperature sensitivity in the 250–450 K temperature range allows using the Pr3+:LiGdF4 phosphors for biological and industrial applications. The relatively low specific heat minimizes the impact of the phosphors on the studied object for which the temperature reading is performed.

Synthesis and study of a new mixed-layered compound GeBi3Te4 belonging to the nBi2–mGeBi2Te4 homologous series

In light of the structural properties of tetradymite-like layered chalcogenide compounds, the mixed-layered compound GeBi3Te4 was predicted and synthesized for the first time, which belongs to the nBi2–mGeBi2Te4 homologous series in the Ge-Te-Bi system. A polycrystal of a new phase was synthesized, and its single crystal was grown by the Bridgman–Stockbarger method. The obtained samples were investigated by differential thermal analysis (DTA) and powder X-ray diffraction (XRD). It was found that the compound melts peritectically at 563 C and has a rhombohedral lattice-type structure with the following lattice parameters: a =4.3625 (5) Å, c = 31.381 (2) Å (sp. gr R3m). The crystal structure of the layered van der Waals compound GeBi3Te4 consists of a repetition of seven-layer GeBi2Te4 packets and two-layer Bi packets in the form of -7-2-7-7-2-7-7-2-7- which differ from the previously discovered GeBi4Te4 phase, which consists of unit cells from only one seven-layer packet. The discovery of a new mixed-layered compound indicates the possibility of the formation of similar compounds in AIV–BV–Te (AIV = Ge, Sn, Pb; BV = Sb, Bi) systems

Experimental and computational investigations of 4, 4′-Dimethoxybenzoin single crystal for optical limiting applications

High quality organic single crystals of 4, 4′-Dimethoxybenzoin (4,4′-DMB) were grown by Bridgman technique by optimizing the growth conditions. Single-phase formation of the compound without any impurities and unit cell parameters were found by powder X-ray diffraction. Photo luminescence spectra showed green emission in the grown crystal. DFT computations on the optical and structural properties were matching with the experimental findings. The cut off wavelength of the grown crystal was found to be around 346 nm and optical bandgap is found to be 2.7 eV.VickersMicrohardness (Hv) measurements revealed of the 4,4, DMB single crystal shown the soft material category. Laser damage threshold studies for the grown crystals were done and compared with other NLO crystals. The optical nonlinear property of the grown crystal were analyzed by Z-scan technique.

Growth of 6Li-enriched LiCl/BaCl2 eutectic as a novel neutron scintillator

In this study, Eu:6LiCl/BaCl2 with a high Li concentration was developed as a novel thermal neutron scintillator. Eu ions were doped as activators for the BaCl2 phase, and Eu:6LiCl/BaCl2 eutectics were grown via the vertical Bridgman–Stockbarger method in quartz ampoules (inner diameter = 4 mm). The Eu:6LiCl/BaCl2 eutectic exhibited a lamellar eutectic structure and optical transparency. The 400 nm emission due to the Eu2+ 4f–5d transition was observed in the BaCl2 phase by a cathode luminescence measurement. The light yield under neutrons was estimated to be over 20 200 photons MeV−1. A PSD study was also performed using gamma and alpha-rays. The Eu:6LiCl/BaCl2 eutectic scintillator showed good potential for PSD.