Growth and optical damage resistance of Sc,Er Co‐doped LiNbO3 crystals

A series of Sc:Er:LiNbO₃ crystals have been grown by Czochralski method. Their ultraviolet‐visible (UV‐Vis) absorption spectra was measured and discussed to investigate their defect structure. The optical damage resistance of Sc:Er:LiNbO₃ crystals was characterized by the transmitted beam pattern distortion method. It increases remarkably when the concentration of Sc₂O₃ exceeds a threshold concentration. The optical damage resistance of Sc (3.0mol %):Er:LiNbO₃ is much higher than that of the Er:LiNbO₃. The intrinsic and extrinsic defects were discussed to explain the enhance of the optical damage resistance in the Sc:Er:LiNbO₃ crystals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structure and electrical resistance of thin scandium films (III). Study on electrical properties

The specific resistance-thickness of ScH_x (vacuum 10⁻⁵ to 5 · 10⁻⁶ Torr) and Sc films (vacuum 1 · 10⁻⁸ to 3 · 10⁻⁸ Torr) relationships have been obtained by keeping a record of a film resistance directly in the course of condensation. The results are discussed according to the theory FUCHS -SONDHEIMER (ScH_x, Sc) and MAYADAS -SHATZKES (Sc) assuming a diffuse scattering of the carriers (P = 0) on the external surface of the films. A mean free path of the current carriers is 188 to 355 Å (T ⋍ 300 K) for ScH_x and 400 Å with grain-boundary scattering parameter from 0.1 to 0.3 for Sc. The temperature dependence of specific resistivity of Sc films was obtained in the interval from 300 to 650 K during the annealing in vacuum 5 · 10⁻⁹ Torr.     

The structure of the scandium iodide complex with antipyrine (AP) and its comparison with the structure of nonisostructural analogues (Compounds [Ln(AP)6]I3 (Ln = La, Y, or Eu))

An X-ray diffraction study of the scandium iodide complex with antipyrine [Sc(AP)₆]I₃ (AP is antipyrine, i.e., 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) (I), which is not isostructural to the analogous compounds of Y, La, and Eu (II), is performed. Crystals I are trigonal; a = 24.911 ? and c = 10.140 ?; Z = 3, space group P $ \bar 3 $ \bar 3 . Crystal I is built of [Sc(AP)₆]³⁺ complex cations of two types and I⁻ anions. In both cations, the Sc atom is octahedrally coordinated by six O atoms of six AP ligands (Sc-O, 2.054–2.078 ?). Complexes I differ from II by the absence of π-π stacking interactions between AP molecules, resulting in a supramolecular cation. Complex cations I of both types form combined layers. All I⁻ anions are located in the interlayer space, being statistically disordered within a flat area limited by eight complex cations of Sc1 and Sc2.     

The Description of the Isothermal Decomposition Processes in Al?Sc Alloys by means of Electric Resistivity Measurements and TEM Investigations

The decomposition behaviour of two AlSc alloys (c_Sc = 0.18; 0.36 at.%) after direct quench to room temperature and subsequent ageing at temperatures in the range 200 °C ≦ T_a ≦ 550 °C was investigated by means of isothermal resistivity measurements and TEM. In the temperature range 325 °C ≦ T_a ≦ 400 °C both alloys show independent of the Sc content an “inversion” of the decomposition kinetics, obviously caused by the transition of the coherent into the incoherent Al₃Sc phase.     

Czochralski growth of Lu1‐xScxBO3:Ce solid solution crystals

Single crystals of Lu_1‐xSc_xBO₃:Ce (x=0.2, 0.3, 0.5, 0.7) were grown by Czochralski method. Continuous solid solution with calcite structure and a linear compositional dependency of crystal lattice parameter in the system Lu_1‐xSc_xBO₃:Ce are formed and their symmetry belong to hexagonal system with R3c space group checked by X‐ray powder diffraction. The electron probe micro‐analysis measurements show that the main inclusions in Lu_1‐xSc_xBO₃:Ce crystals are in the form of Sc rich oxide and Ce rich oxide. The ICP‐AES tests show that the more Sc ion content in Lu_1‐xSc_xBO₃:Ce, the smaller effective segregation coefficient of Ce in crystal will be. The X‐ray excited luminescence spectra of Lu_1‐xSc_xBO₃:Ce crystals all present a double peaked emission band with maxima round 370 and 400 nm corresponding to Ce³⁺ emission and a self trapped excitons (STE) band peaking at 269 nm. In addition, due to high density, high relative light yield, fast decay time and no‐hygroscopic property, Lu_0.8Sc_0.2BO₃:1 at%Ce crystal could be a good candidate material for scintillation application by improving the crystal quality and cerium concentration. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the scandium distribution in indium arsenide crystals grown by the Czochralski method

In this paper the behaviour of scandium in n-type monocrystalline indium arsenide grown by Czochralski method in sealed ampoule is studied. The crystals have been grown in [111] direction under different conditions: crystallization rate, As-partial pressure and scandium initial concentration in the melt. The effect of the above factors on the scandium distribution along the crystals have been investigated. Using these results and by means of the equation of normal freezing the effective Sc distribution coefficient (k) in InAs under different technological conditions has been determined. It has been found that k < 1 in all experiments. In order to find the equilibrium coefficient (k₀) at fixed growth conditions the Burton-Prim-Slichter model has been used. On the basis of Hall measurements and atomic absorption analysis of Sc-doped InAs it is concluded that connected with Sc electrically active centers behave as shallow donors, most probably monovalent ones.     

X-ray diffraction study of amorphous alloys Al–Ni–Ce–Sc with using Ehrenfest’s formula

The effect of replacement of Ce by Sc in the amorphous Al₈₅Ni₁₀Ce₅ alloy on its structure has been studied. The replacement was shown to result in increasing the coordination number in the first coordination sphere, changing the type of short-range order. A splitting the first peak of the function of radial atom distribution into two subpeaks made it possible to determine separately the coordination number for the atom pair groups Ce–Al, Sc–Al, Al–Al and Ni–Al, Al–Al. The structure of the amorphous alloys Al₈₅Ni₁₀Ce_5−xSc_x (x = 0, 1, 5) was determined using X-ray diffractometry combined with application of Ehrenfest’s formula, which allowed us to directly determine the first coordination sphere radius from data on the structure factor and some cluster parameters obtained from the prepeak on the structure factor curve.     

Quenched glasses containing lanthanum and other trivalent sulfates

A wide glass-forming region has been observed in the Li₂SO₄-La₂(SO₄)₃ system with essentially pure glass produced by roller quenching compositions of 20 to 90% Li. Even water or air quenching produced glasses. Many of these glasses showed double exotherms during crystallization and some showed glass transitions. Limited experiments also showed some glass-formation in other alkali-La sulfates, in compositions containing Y and Sc sulfates and in mixtures. Ionic conductivities and some infrared measurements are also reported.     

Scandium thin films-structure and electrical resistance (I). A study on films obtained in a vacuum of 10−5 up to 10−6 Torr

A structure as well as a specific electrical resistance of scandium films having a various thickness (300 up to 2800 Å) obtained at a condensation rate: w⋍ 1 up to 155 Å/s have been studied in the present work. Depending on condensation conditions in films a hydride ScH_x, h.c.p. — Sc, or ScH_x + Sc alternatively, is formed, a phase containing a distorted hexagonal lattice evolving into the ScH_x over a period of a few hours. The ScH_x and h.c.p-Sc change to Sc₂O₃ when annealed in a vacuum of 5 · 10⁻⁵ Torr at a T ≈ 800°C, while in a vacuum of 3 · 10⁻⁸ Torr a change to h.c.p.-Sc with negligible inclusions of oxidic Sc₂O₃ particles takes place. Formation of oxide is observed also when heating the films with an electron beam directly in a microscope under vacuum of ∼ 8 · 10⁻⁵ Torr. The specific electrical resistance ϱ of the film just after a condensation has taken place is approximatly by an order higher as against the ScH_x- and h.c.p.-Sc solid specimens. An irreversible gain in said resistance is observed while holding at a room temperature or annealing in a vacuum of 5 · 10⁻⁵ Torr, this being associated with absorption of H₂, O₂ and, possibly, of water steam, and then with formation of Sc₂O₃. Annealing in a vacuum of 5 · 10⁻⁸ up to 10⁻⁷ Torr involves a temperature relationship for ϱ of an intricated nature, this being accounted for by a structure transition as follows: A diode-effect diminishing with a temperature rise is observed in annealed films.     

Investigation of multicomponent fluoride optical materials in the UV spectral region: I. Single crystals of Ca1−x R xF2+x (R = Sc, Y, La, Yb, Lu) solid solutions

Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca_1?x R _xF_2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region.     

Radiation resistance of endohedral metallofullerenols under neutron irradiation

The endohedral metallofullerenols Me@C_2n(OH)_38–40 + C_2n(OH)_38–40 (Me = Tb, Sc, Gd, Fe, Pr, Mo) have been obtained and their radiation resistance under irradiation by a neutron flux of 8 × 10¹³ cm^–2 s^–1 has been studied. The factors affecting the radiation resistance of endohedral metallofullerenols are discussed.     

The crystal and molecular structure of a trifluoroacetylacetonate complex of scandium,Sc(CH<Subscript>3</Subscript>COCHCOCF<Subscript>3</Subscript>)<Subscript>3</Subscript>

The crystal and molecular structure of Sc(CH₃COCHCOCF₃)₃ has been determined by X-ray diffraction. The compound crystallizes as pure mer-isomer in the orthorhombic space group Pbca with lattice parameters a=15.166(8) ?, b=13.560(7) ?, c=19.327(10) ?, α=β=γ=90°, V=3974(4) ?³, Z=8. The complex at 100 K is partially disordered in the crystal structure in an approximate 5:1 ratio with 83% fluorine population at C-11 and 17% at C-15. NMR data is compared to that previously reported.     

Ultraviolet Photoelectron Spectra of Mono Metal Atom Encapsulated Fullerenes

Abstract

Ultraviolet photoelectron spectra of mono metal atom encapsulated fullerenes, M@C₈₂ (M = La, Gd and Sc), are measured with a synchrotron radiation light source. When the excitation energy is tuned, spectral intensity oscillation is observed in these mono metal atom encapsulated fullerenes as was in empty fullerene, C₈₂. Their incident photon energy dependence is essentially the same. Their spectra deeper than 5 eV are almost identical and are similar to those of empty fullerene. The noticeable difference among the spectra is in the energy region between the Fermi level and 4 eV, which reveals the degree of electron transfer from the metal atom to the fullerene cage.     

Search for compounds of the NaBaR(BO3)2 family (R = La, Nd, Gd, and Yb) and the new NaBaYb(BO3)2 orthoborate

A search for compounds of the NaBaR(BO₃)₂ composition (where R = La³⁺, Nd³⁺, Gd³⁺, or Yb³⁺) is performed by solid state synthesis and spontaneous crystallization. A new compound, NaBaYb(BO₃)₂, is found in this series. It crystallizes in space group $R\bar 3$ and belongs to the family of sublayer complex orthoborates with isolated BO₃ groups NaBaR(BO₃)₂ (R = Y, Sc, and Yb). Theoretical X-ray powder diffraction patterns of NaBaY(BO₃)₂, NaBaSc(BO₃)₂, and NaBaYb(BO₃)₂ are calculated based on single-crystal data.     

New framework hydrous silicate K3Sc[Si3O9] · H2O related to the high-temperature anhydrous silicate K3Ho[Si3O9] and symmetry analysis of a phase transition with prediction of structures

Crystals of a new framework silicate K₃Sc[Si₃O₉] · H₂O, space group Pm2₁ n (nonstandard setting of space group Pmn2₁ = C _2v ⁷), are obtained under hydrothermal conditions. The structure is determined without preliminary knowledge of the chemical formula. The absolute configuration is determined. The structure is close to that of the high-temperature K₃Ho[Si₃O₉] phase, which was obtained upon the heating of K₃HoSi₃O₈(OH)₂. This structural similarity is due to the specific conditions of synthesis and an analogous formula, where holmium is replaced by scandium. A symmetry analysis shows that the high local symmetry of a block (rod) is responsible for the first-order phase transition of both the order-disorder (OD) and displacement type. The number of structures in which the simplest and high-symmetry layers are multiplied by different symmetry elements are predicted.     

New garnet crystal potentially suited for mini-laser devices of 1.5-μm spectral range

In Er:doped crystals, the 1.5-μm (⁴I_13/2–⁴I_15/2) transition is of negligibly small intensity. To intensify this transition, the (Gd,Y)₃(Ga,Sc)₅O₁₂ host crystal has been chosen as a basic medium. The single crystal garnet films with thickness up to 18-μm were grown using the method of liquid-phase epitaxy on Gd₃Ga₅O₁₂ substrates. The 20-at.% maximal concentration of Er³⁺-ions was achieved without luminescence quenching. The up-conversion processes were neutralized by the addition of an Fe-ions sensitizer. At the same level of absorbed pumping power, the luminescence intensity at the 1.5-μm band for the Er:Fe:doped crystal was approximately one to two orders of magnitude higher than that for traditional content. Heavily doped crystals demonstrated broadening of the luminescence band up to 300 nm.     

Synthesis and radiation resistance of fullerenes and fullerene derivatives

The parameters of an electric-arc facility for the synthesis of fullerenes and endohedral metallofullerenes are optimized. The resistance of С₆₀ and С₇₀ fullerenes and С₆₀(ОН)₃₀ and С₇₀(ОН)₃₀ fullerenols against neutron irradiation is studied. It is established that the radiation resistance of the fullerenes is higher than that of the fullerenols, but the radiation resistance of the Gd@C_2n endometallofullerenes is lower than that of the corresponding Gd@C_2n(OH)₃₈ fullerenols. The radiation resistance of mixtures of Ме@C_2n(OH)₃₈ (Me = Gd, Tb, Sc, Fe, and Pr) endometallofullerenes with C₆₀(OH)₃₀ is determined. The factors affecting the radiation resistance of the fullerenes and fullerenols are discussed.     

Determination of Mass Transfer Coefficients for Crystal Growth of Nitrate Salts

In this paper, the crystal growth of sodium nitrate and potassium nitrate from aqueous solutions, in a perfectly stirred batch crystallizer, has been studied considering the effect of temperature, supersaturation degree, and the size of seed crystal growth rate. The mass transfer coefficients obtained correlated with Re, Sc and NL dimensionaless numbers. Supersaturation curve determination using a 0.5 mW He-Ne laser, connected to an automated data acquisition system, was the first stage of the study. The supersaturation and saturation curves were closely parallel with average DT value of 4.1 and 6.8 °C for KNO₃ and NaNO₃ respectively. For the growth kinetics order, unit values were found for both salts, with diffusion as a controlling stage.     

Mixed tetrahedral anionic framework in the K3Ga2(PO4)3 crystal structure

The crystal structure of a new synthetic potassium gallophosphate K₃Ga₂(PO₄)₃ grown from a solution in the melt of a mixture of GaPO₄ and K₂MoO₄ is determined using X-ray diffraction (Bruker Smart diffractometer, 2θ_max= 56.6°, R = 0.044 for 2931 reflections, T = 100 K). The main crystal data are as follows: a = 8.661(2) Å, b = 17.002(4) Å, c = 8.386(2) Å, space group Pna2₁, Z= 4, and ρ_calcd = 2.91 g/cm³. The synthesized crystals represent the third phase in the structure type previously established for the K₃Al₂[(As,P)O₄]₃ compound. It is shown that the structure consists of a three-dimensional anionic microporous tetrahedral framework of the mixed type, which is formed by PO₄ and GaO₄ tetrahedra shared by vertices. Large-sized cations K⁺ occupy channels of the zeolite-like framework. The crystal chemical features of the formation of structure types of compounds with mixed frameworks described by the general formula A ₃ ⁺ M ₂ ³⁺ (TO₄)₃ (where A = K, Rb, (NH₄), Tl; M = Al, Ga, Fe, Sc, Yb; T = P, As) are analyzed.     

Structural Report for Sc[(R,R)-norephedrine-pybox](OTf)3 Dimeric Complex

Abstract The title compound containing two metal centers each complexes to one enantiopure chiral norephedrine-derived pyridyl-(bis) oxazoline (pybox) ligand and linked by two hydroxide bridges, crystallizes to give rodlike form in the space group P2₁(# 4). Cell Parameters are a = 10.2344(18) ?, b = 13.952(3) ?, c = 23.371(4) ?, β = 94.586(4)°, V = 3326.6(10) ?³. The metal-hydroxide motif forms a square plane at the center of the structure with the scandium centers exhibiting a distorted pentagonal bipyramid coordination sphere consisting of the chelating ligand and two additional triflouromethyl sulfonyloxy species positioned anti to each other. Graphical abstract The complex contains two metal centers each complexes to one enantiopure chiral norephedrine-derived pyridyl-(bis) oxazoline (pybox) ligand and linked by two hydroxide bridges. Structural report for Sc[(R,R)-norephedrine-pybox](OTf)₃ dimeric complex Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.