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Bart Kahr - One of the best experts on this subject based on the ideXlab platform.

  • Structure and optical characterization of Rochelle salt dye inclusion Crystals and the fluorescence detection of their phase transitions
    Ferroelectrics, 1997
    Co-Authors: Salah S. Sedarous, J. Anand Subramony, Bart Kahr
    Abstract:

    Abstract We describe the growth and spectroscopy of well-defined Mixed Crystals of sodium potassium tartrate (Rochelle salt) containing synthetic organic dyes in the {010} growth sectors. Our summary reevaluates historical dye inclusions and reveals others that we discovered. Absorption and emission spectroscopies with polarized light are used to characterize these Mixed Crystals. The temperature dependence of the fluorescence of included chromophores provide evidence of the ferroelectric phase transitions in the host Crystals.

  • reevaluating structures for Mixed Crystals of simple isomorphous salts sodium chlorate bromate naclxbr1 xo3
    Journal of the American Chemical Society, 1993
    Co-Authors: Prakash Gopalan, Matthew L Peterson, Guy Crundwell, Bart Kahr
    Abstract:

    Evidence has accumulated recently supporting the notion that structures of solid solutions have been misunderstood since the inception of X-ray diffraction.’ Flags abound in the crystallographic record that signal caution when examining Mixed Crystals grown under kinetic control.2 This is particularly true of the optical descriptions of the many Crystals whose morphologies are at variance with their optical properties.3 Therefore, we began structural studies of Mixed Crystals of simple isomorphous salts,4 including NaC103 and NaBr03.5 NaC1,Brl_,03, previously studied by X-ray diffraction and formerly treated as ideal, cubic, solid solutions, reveal secondary low-symmetry structures heretofore unappreciated. The structures question the general applicability of the Law of Isomorphism to Mixed Crystals. Anomalous birefringence in cubes of NaC103 was first observed by Mitscherlich in 18466 and commented on subsequently’ for NaC1,Brl.,03. Mitscherlich’s greatest contribution, the Law of Isomorphism,8 was based on the observation that some simple crystalline salts could be Mixed without affecting habit; ions were exchanged willy-nilly, seemingly without affecting s t r ~ c t u r e . ~ Our intuition about solid solutions is inherited from him-the solute should be distributed randomly. I The optical anisotropy in NaC1,BrI_,O3 implies a reduction from cubic symmetry, but unfortunately it has been hard to interpret. Brauns said that the Crystals look “so complicated, that I have not obtained a clear p i c t ~ r e ” . ~ ~ Recent observers treated the birefringence as a nuisaxe. l o We reproduced birefringent NaC1,Brl_,03 Crystals by evaporating water solutions of varying composition. Crystals were selected from large reservoirs. Compositional homogeneity was confirmed by analyzing for Br03-. Solutions made from frag-

U Fawad - One of the best experts on this subject based on the ideXlab platform.

  • czochralski growth and scintillation properties of li 6 lu x y 1 x bo 3 3 ce 3 single Crystals
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2016
    Co-Authors: U Fawad, H J Kim, H Park, Sunghwan Kim, Sajid Khan
    Abstract:

    We report on Czochralski growth of Ce3+-doped Mixed Crystals of Li6Lu(BO3)3 (LLBO) and Li6Y(BO3)3 (LYBO) i.e. Li6LuxY1−x(BO3)3 (x=0.0, 0.5, 1.0) (LLYBO). Problems faced during the growth process and the techniques to overcome them are discussed. Single phase of the grown Crystals is confirmed by powder X-ray diffraction (XRD) analysis. The grown Crystals are characterized for their scintillation properties such as energy resolution, light yield, fluorescent decay time and α/β ratio under γ-rays and α-particles excitation. The X-ray induced luminescence is measured for the grown Crystals.

  • crystal growth and scintillation properties of li 6 lu x gd 1 x bo 3 3 ce 3 single Crystals
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2014
    Co-Authors: U Fawad, H J Kim, Gul Rooh, H Park, Sunghwan Kim, Hua Jiang
    Abstract:

    Mixed Crystals of Li6Gd(BO3)3 and Li6Lu(BO3)3, Li6LuxGd1−x(BO3)3, doped with Ce3+ ion are grown by the Czochralski technique (x=0.0, 0.2, 0.5, 0.8, 1.0). The growth problems during the crystal growth process and the technique to overcome them are discussed in detail. Powder X-ray diffraction (XRD) analysis confirms single phase of all the grown samples. Laser induced luminescence spectra are presented. Scintillation properties such as energy resolution, light yield, decay time and α/β ratio under the excitation of γ-rays and α-particles are also presented.

  • on the growth and scintillation properties of li 6 lu x gd 1 x bo 3 3 ce 3 where x 0 0 0 2 0 5 0 8 1 0
    Nuclear Science Symposium and Medical Imaging Conference, 2013
    Co-Authors: U Fawad, H J Kim, Gul Rooh, H Park, Sunghwan Kim, Hua Jiang
    Abstract:

    We have grown Mixed Crystals of Li 6 Gd(BO 3 ) 3 and Li 6 Lu(BO 3 ) 3 , Li 6 Lu x Gd 1−x (BO 3 ) 3 , doped with 3 mol% of Ce3+ ion by Czochralski technique (x = 0.0, 0.2, 0.5, 0.8, 1.0). In this paper we have discussed the growth problems during the crystal growth and technique to overcome. Powder X-ray diffraction (XRD) analysis have confirmed single phase of all the grown Crystals. X-ray induced luminescence spectra are presented. Scintillation properties are presented as well such as; such as energy resolution, light yield and decay time under the excitation of γ-rays and α-particles.

Hua Jiang - One of the best experts on this subject based on the ideXlab platform.

  • crystal growth and scintillation properties of li 6 lu x gd 1 x bo 3 3 ce 3 single Crystals
    Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2014
    Co-Authors: U Fawad, H J Kim, Gul Rooh, H Park, Sunghwan Kim, Hua Jiang
    Abstract:

    Mixed Crystals of Li6Gd(BO3)3 and Li6Lu(BO3)3, Li6LuxGd1−x(BO3)3, doped with Ce3+ ion are grown by the Czochralski technique (x=0.0, 0.2, 0.5, 0.8, 1.0). The growth problems during the crystal growth process and the technique to overcome them are discussed in detail. Powder X-ray diffraction (XRD) analysis confirms single phase of all the grown samples. Laser induced luminescence spectra are presented. Scintillation properties such as energy resolution, light yield, decay time and α/β ratio under the excitation of γ-rays and α-particles are also presented.

  • on the growth and scintillation properties of li 6 lu x gd 1 x bo 3 3 ce 3 where x 0 0 0 2 0 5 0 8 1 0
    Nuclear Science Symposium and Medical Imaging Conference, 2013
    Co-Authors: U Fawad, H J Kim, Gul Rooh, H Park, Sunghwan Kim, Hua Jiang
    Abstract:

    We have grown Mixed Crystals of Li 6 Gd(BO 3 ) 3 and Li 6 Lu(BO 3 ) 3 , Li 6 Lu x Gd 1−x (BO 3 ) 3 , doped with 3 mol% of Ce3+ ion by Czochralski technique (x = 0.0, 0.2, 0.5, 0.8, 1.0). In this paper we have discussed the growth problems during the crystal growth and technique to overcome. Powder X-ray diffraction (XRD) analysis have confirmed single phase of all the grown Crystals. X-ray induced luminescence spectra are presented. Scintillation properties are presented as well such as; such as energy resolution, light yield and decay time under the excitation of γ-rays and α-particles.

Volykhov A.a. - One of the best experts on this subject based on the ideXlab platform.

  • Impact of ordering on the reactivity of Mixed Crystals of topological insulators with anion substitution Bi2SeTe2 and Sb2SeTe2
    2022
    Co-Authors: Volykhov A.a., Frolov A.s., Neudachina V.s., Vladimirova N.v., Gerber E., Callaert C., Hadermann J., Khmelevsky N.o., Knop Gericke A., Nchez Barriga S J.
    Abstract:

    Three dimensional topological insulators TIs are exotic materials with unique properties. Tetradymite type binary chalcogenides of bismuth and antimony, as well as their Mixed Crystals, belong to prototypical TIs. Potential device applications of these materials require in depth knowledge of their stability in the ambient atmosphere and other media maintained during their processing. Here we investigated the reactivity of Mixed Crystals with anion substitution, Bi2 Se1 xTex 3 and Sb2 Se1 xTex 3, towards molecular oxygen using both in situ and ex situ X ray photoelectron spectroscopy. The results indicate that, in contrast to cation substitution, partial substitution of tellurium by selenium atoms leads to anomalously high surface reactivity, which even exceeds that of the most reactive binary constituent. We attribute this effect to anion ordering that essentially modifies the bond geometry, especially the respective bond angles as modeled by DF

  • Can surface reactivity of Mixed Crystals be predicted from their counterparts? A case study of Bi1 xSbx 2Te3 topological insulators
    2018
    Co-Authors: Volykhov A.a., Neudachina V.s., Vladimirova N.v., Callaert C., Hadermann J., Nchez Barriga S J., Batuk M., Sirotina A.p., Belova A.i., Tamm M.e.
    Abstract:

    The behavior of ternary Mixed Crystals or solid solutions and its correlation with the properties of their binary constituents is of fundamental interest. Due to their unique potential for application in future information technology, Mixed Crystals of topological insulators with the spin locked, gapless states on their surfaces attract huge attention of physicists, chemists and material scientists. Bi1 amp; 8722;xSbx 2Te3 solid solutions are among the best candidates for spintronic applications since the bulk carrier concentration can be tuned by varying x to obtain truly bulk insulating samples, where the topological surface states largely contribute to the transport and the realization of the surface quantum Hall effect. As this ternary compound will be evidently used in the form of thin film devices its chemical stability is an important practical issue. Based on the atomic resolution HAADF TEM and EDX data together with the XPS results obtained both ex situ and in situ, we propose an atomistic picture of the Mixed crystal reactivity compared to that of its binary constituents. We find that the surface reactivity is determined by the probability of oxygen attack on the Te Sb bonds, which is directly proportional to the number of Te atoms bonded to at least one Sb atom. The oxidation mechanism includes formation of an amorphous antimony oxide at the very surface due to Sb diffusion from the first two quintuple layers, electron tunneling from the Fermi level of the crystal to oxygen, oxygen ion diffusion to the crystal, and finally, slow Te oxidation to the 4 oxidation state. The oxide layer thickness is limited by the electron transport, and the overall process resembles the Cabrera Mott mechanism in metals. These observations are critical not only for current understanding of the chemical reactivity of complex Crystals, but also to improve the performance of future spintronic devices based on topological material

  • Can surface reactivity of Mixed Crystals be predicted from their counterparts? A case study of (Bi1−xSbx)2Te3 topological insulators
    'Royal Society of Chemistry (RSC)', 2018
    Co-Authors: Volykhov A.a., Callaert C., Hadermann J., Batuk M., Sánchez-barriga J., Sirotina A., Belova A., Vladimirova N., Tamm M.
    Abstract:

    The behavior of ternary Mixed Crystals or solid solutions and its correlation with the properties of their binary constituents is of fundamental interest. Due to their unique potential for application in future information technology, Mixed Crystals of topological insulators with the spin-locked, gapless states on their surfaces attract huge attention of physicists, chemists and material scientists. (Bi1−xSbx)2Te3 solid solutions are among the best candidates for spintronic applications since the bulk carrier concentration can be tuned by varying x to obtain truly bulk-insulating samples, where the topological surface states largely contribute to the transport and the realization of the surface quantum Hall effect. As this ternary compound will be evidently used in the form of thin-film devices its chemical stability is an important practical issue. Based on the atomic resolution HAADF-TEM and EDX data together with the XPS results obtained both ex situ and in situ, we propose an atomistic picture of the Mixed crystal reactivity compared to that of its binary constituents. We find that the surface reactivity is determined by the probability of oxygen attack on the Te–Sb bonds, which is directly proportional to the number of Te atoms bonded to at least one Sb atom. The oxidation mechanism includes formation of an amorphous antimony oxide at the very surface due to Sb diffusion from the first two quintuple layers, electron tunneling from the Fermi level of the crystal to oxygen, oxygen ion diffusion to the crystal, and finally, slow Te oxidation to the +4 oxidation state. The oxide layer thickness is limited by the electron transport, and the overall process resembles the Cabrera–Mott mechanism in metals. These observations are critical not only for current understanding of the chemical reactivity of complex Crystals, but also to improve the performance of future spintronic devices based on topological materials

Tomas Šalkus - One of the best experts on this subject based on the ideXlab platform.

  • temperature and compositional behaviour of electrical conductivity and optical absorption edge in cu7ge s1 xsex 5i Mixed superionic Crystals
    Solid State Ionics, 2010
    Co-Authors: I. P. Studenyak, M. Kranjcec, V.v. Bilanchuk, O.p. Kokhan, Antanas Feliksas Orliukas, A. Kezionis, Edvardas Kazakevičius, Tomas Šalkus
    Abstract:

    Abstract Electrical and optical properties of Cu 7 Ge(S 1 − x Se x ) 5 I Mixed Crystals, grown by chemical vapour transport, are studied. Compositional dependencies of their electrical conductivity, measured in the frequency range 1.0 ⋅ 10 6 –1.2 ⋅ 10 9  Hz at 100–300 K and the corresponding activation energy, are analysed. The optical absorption edge of Cu 7 Ge(S 1 − x Se x ) 5 I Mixed Crystals is studied in the temperature range 77–300 K, the compositional dependencies of the optical pseudogap and Urbach energy being obtained. The effect of different types of disordering on the optical absorption processes at S → Se anionic substitution in the Cu 7 Ge(S 1 − x Se x ) 5 I Mixed Crystals is investigated.