Temperature dependence of the quadratic electrooptic effect and estimation of antipolarization of ADP

Measurements of the temperature dependence of the quadratic electrooptic coefficient |g₁₁₁₁‐g₂₂₁₁| of ADP were made. The coefficient is found to decrease with an increase in temperature. The results show that the intrinsic quadratic electrooptic coefficient |M₁₁₁₁‐M₂₂₁₁| defined in terms of polarization also dependes on temperature. Employing the temperature dependence of |M₁₁₁₁‐M₂₂₁₁| estimation of antipolarization in lowtemperature antiferroelectric phase of ADP is made. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Angular stability of electric field‐induced effects in crystalline materials

We analyze angular bandwidths of extrema of the indicative surfaces describing spatial anisotropy of piezoelectric (PE) and electrooptic (EO) properties of doped lithium niobate (LiNbO₃:MgO) and langasite (La₃Ga₅SiO₁₄) crystals. A number of highly efficient experimental geometries are suggested, which are promising for PE and EO devices. Our data obtained with both analytical and numerical techniques characterize angular stability of those devices and, in particular, their angular aperture. We show that, besides of a maximal size of the electric field‐induced effects, ‘nondirect crystal cuts’ offer considerably higher angular stability of their characteristics, when compared with that typical for ‘direct crystal cuts’ usually employed in PE and EO devices.     

Growth and characterization of La3Ga5.5Ta0.5O14 crystal

La₃Ga_5.5Ta_0.5O₁₄ (LGT) crystal was grown by using the Czochralski method. The as‐grown crystal is transparent, free from inclusions and with no cracks. Specific heat, thermal expansion, dielectric constants, transmission spectrum and optical damage threshold of LGT have been measured, and the results show general properties of LGT are similar to that of La₃Ga₅SiO₁₄ (LGS) crystal. The experiment to research the Q‐switch properties of LGT has been performed and the results show LGT possesses smaller electrooptic coefficients than that of LGS and may not be an ideal material used as a Q‐switch. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth process and optical investigations of Nd:NaGd (MoO4)2 crystals with varying content of Nd and Gd

In this paper, [NaGd_1‐xNdx](MoO₄)₂ crystals with x = 0.005–0.05 were grown by Czochralski method at 950 ℃ for 10 hours and subsequently characterized by absorption spectroscopy and fluorescence spectroscopy. The intensity parameters of Nd³⁺ were calculated by Judd‐Ofelt theory, and the relationship between the parameters and Nd³⁺ concentration was analyzed. The results show that with the increasing Nd³⁺ concentration, the oscillator strength, stimulated emission cross‐section, Ω_t and spontaneous transition probability decrease slightly, while the fluorescence lifetime decreases significantly. However, the fluorescence branching ratio is almost unchanged with the increasing Nd³⁺concentration. The [NaGd_1‐xNd_x](MoO₄)₂ crystal with (x = 0.01) possesses the highest quantum efficiency of 88.98%, a good fluorescence line‐width of 23 nm, a large value of σ_em·τ_f up to 0.55 × 10⁻²² cm²·s and a stimulated emission cross‐section up to 3.747 × 10⁻¹⁹ cm² for the transition from ⁴F_3/2 to⁴I_11/2 at 1064 nm. Test results indicate that [NaGd_1‐xNd_x](MoO₄)₂ crystals are an excellent gain media for the solid state laser system.     

MOLECULAR AND COLLECTIVE PROCESSES IN THE ANTIFERROELECTRIC PHASE OF A CHLORINATED COMPOUND

Abstract

New liquid crystalline substance, (S) 4-(1-methylheptyloxycarbonyl)-3-chlorophenyl 4′-(4-butanoiloxybut-1-oxy)biphenyl-4-carboxylate, exhibiting ferroelectric and antiferroelectric phases have been studied by means of frequency domain dielectric spectroscopy. DSC calorimetric and electrooptic measurements were done to study its phase transitions and electrooptic behaviour. In the antiferroelectric SmC_A* phase one of the dielectric relaxation modes exhibits a non-Arrhenius behaviour. The plots of critical frequencies and dielectric increments vs. temperature show an anomalous behaviour of the relaxation processes in the neighbourhood of the ferroelectric — antiferroelectric phase transition. Reversal current method reveals one current peak in the ferroelectric phase and two in the antiferroelectric one. Temperature dependencies of tilt angle, spontaneous polarization, switching time and transmittance are also presented and discussed in scope of the mean-field theory.     

Synthesis and structure of a new one‐dimensional cobalt complex with dicyanamide and 4‐picolyl choride bridges

The synthesis and structure of the 1D cobalt (II) complex, [Co( L )₂(dca)₂] ( 1 ) (dca = dicyanamide, C₂N₃^–, L = 4‐picolyl choride) is reported. Complex 1 crystallized in triclinic system, space group P ‐1, with cell dimensions of a = 7.291(2) Å, b = 7.481(2) Å, c = 9.007(3) Å, α =104.444(4)°, β = 96.971(4)°, γ =102.618(4)°, V = 456.1(2) ų, Z = 1, Dc = 1.624 Mg/m³. In complex 1 , Co (II) is 6‐coordinated by N atoms of four dca ligands and two L ligands. The centrosymmetric CoN6 chromophore is an axially elongated octahedron that has Co‐N distances ranging from 2.122(3) to 2.154(3) Å. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal properties of a Nd:LuVO4 crystal

A Nd‐doped lutetium orthovanadate Nd:LuVO₄ crystal has been grown using a modified Czochralski method. The thermal properties of this crystal have been studied by measuring the thermal expansion, specific heat and thermal diffusivity. The thermal expansion coefficients are α₁₁ = 1.7 × 10^‐6, α₂₂ = 1.5 × 10^‐6 and α₃₃ = 9.1 × 10^‐6/K in the temperature range of 298–573 K along the three respective crystallographic axes. The specific heat is almost linear and increases from 0.442 to 0.498 Jg^‐1K^‐1 in the measured temperature range. The thermal diffusivity is anisotropic and decreases with increasing temperature from 295 to 548 K. At room temperature the calculated thermal conductivities κ₁₁ and κ₃₃ are 7.96 and 9.77 Wm^‐1K^‐1, respectively. These thermal parameters of Nd:LuVO₄ crystal have indicated that it is an excellent candidate laser material. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,characterization and crystal structure of a novel 2D Ni(II) complex with malate

An exploration of the nickel‐ malate‐bpa system under hydrothermal conditions, has led to the isolation of a novel framework {[Ni(Hmal)(bpa)]·2.5H₂O}_n ( 1 ) (Hmal = malate dianion, bpa = 1,2‐bi(4‐pyridyl)ethane). Single‐crystal X‐ray analyses reveal that it crystallizes in the orthorhombic space group Fdd2. a = 21.9944(13) Å, b =33.3369(19) Å, c = 10.3969(5) Å, β = 90°. The Ni^II ions are linked into an extended helical chain via Hmal molecules. Further these chains are united together through the bridging bpa to form a 2D grid layer, which exhibits a typical (6,3) topological network. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,thermophysical and electrical properties of the nonlinear optical crystal BPO4

Bulk BPO₄ crystals have been successfully grown from high temperature solution of BPO₄, Li₂O, and MoO₃ in the molar ratio of 2.3:1:1.3 by the top‐seeded solution growth (TSSG) method using [101]^c orientation seeds. There are no visible scattering centers and impurity of Mo in the as‐grown BPO₄ crystals, whose optical homogeneity reaches up to 1.6×10^–5/cm. BPO₄ possesses a specific heat of 0.50–1.00 J·g^–1·K^–1 in the temperature range from 298 to 698 K and exhibits strong anisotropic thermal expansion behavior with α_a = 14.2 × 10^–6 K^–1 and α_c = ‐4.0 × 10^–7 K^–1. Moreover, the thermal conductivity coefficients are calculated to be κ_a = 62.4 W·m^–1·K^–1 and κ_c = 51.5 W·m^–1·K^–1, which are remarkably larger than those of some commonly used borates. The measured dielectric constants, ε_a and ε_c, are 4.8 and 6.1, respectively, and the ionic conductivity coefficients, σ_a = 4.3 × 10^–8 S/cm and σ_c = 9.5 × 10^–8 S/cm, are several orders of magnitude lower than that of LiB₃O₅ (LBO). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Elastic properties of KGd(WO4)2:Ho3+ single crystals studied by Brillouin spectroscopy

The analysis some of the acoustic phonons propagating in pure and Ho³⁺‐doped KGd(WO₄)₂ single crystals in the GHz frequency range by Brillouin scattering method has been presented. For investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101], [101] and [110] have been determined. Moreover, the value of elastic constants C₂₂, C₄₄ and C₆₆ of pure and Ho³⁺‐doped KGd(WO₄)₂ single crystals have been estimated. It was revealed that the presence of the Ho³⁺‐ions in KGd(WO₄)₂ crystals, for the used doping concentration 1 at% and 8 at%, does not influence their elastic properties. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Contribution to the study of elastic properties of KGd(WO4)2:Er3+ single crystals by Brillouin spectroscopy

In this paper we present the study of the acoustic phonons propagating in Er³⁺‐doped KGd(WO₄)₂ single crystals by Brillouin spectroscopy. For the investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101] and [110] have been determined. Moreover, the values of the elastic constants: C₂₂, C₄₄ and C₆₆ of Er³⁺‐doped KGd(WO₄)₂ single crystals have been estimated. It was revealed that the presence of the Er³⁺‐ions in KGd(WO₄)₂ crystals, for the used doping concentration 1 at% does not influence their elastic properties. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Vibrational behavior of matrix‐isolated ions in Tutton compounds IV. Infrared spectroscopic study of NH4+ and SO42‐ ions included in nickel sulfates and selenates

Infrared spectra of K₂Ni(SeO₄)₂·6H₂O and (NH₄)₂Ni(SeO₄)₂·6H₂O containing SO₄^2‐ ions and those of K₂Ni(SO₄)₂·6H₂O and K₂Ni(SeO₄)₂·6H₂O containing NH₄⁺ ions are presented and discussed in the region of ν₃ and ν₁ of the sulfate ions and in the region of ν₄ of the NH₄⁺ ions, respectively. The SO₄^2‐ ions matrix‐isolated in the selenate matrices (approximately 1 mol%) exhibit three bands for ν₃ and one band for ν₁ in agreement with the low site symmetry C₁ of the host selenate ions. The NH₄⁺ guest ions included in the potassium sulfate matrix are characterized also with three bands for ν₄. However, the ammonium ions in (NH₄)₂Ni(SeO₄)₂·6H₂O as well as those included in K₂Ni(SeO₄)₂·6H₂O display four infrared bands corresponding to ν₄ due probably to some kind of disorder of the ammonium ions. The extent of energetic distortion of the isomorphously included sulfate ions as deduced from the values of Δν₃ and Δν_max is commented. The spectroscopic experiments reveal that the SO₄^2‐ guest ions are weaker distorted in the selenate matrices as compared to the same ions in the neat sulfates due to the larger unit‐cell volumes of the selenate compounds. The band positions of the water librations in the host potassium compounds are affected by the included ammonium cations. The formation of hydrogen bonds between the NH₄⁺ guest ions and the XO₄^2‐ host ions leads to a decrease in the proton acceptor capabilities of the anions and as a result the hydrogen bonds weaken on going from the neat potassium compounds to the mixed crystals. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and physical properties of monoclinic L-arginine hydrochloride monohydrate,C6H14O2N4HCl · H2O,and L-arginine hydrobromide monohydrate,C6H14O2N4HBr · H2O

Single crystals of optical quality of L-arginine HCl · H₂O and L-arginine HBr · H₂O with dimensions up to 80 × 60 × 30 mm have been grown from aqueous solutions by controlled evaporation at about 310 K. The isotypic crystals exhibit a quite similar behaviour with respect to morphological, pyroelectric, dielectric, optical, thermal expansion, electrostrictive, electrooptic, elastic, thermoelastic and non-linear optical properties. A distinct anisotropy of the longitudinal elastic stiffness is observed with a maximum along the direction of the alignment of the arginine ions. Nearly in the same direction a minimum of thermal expansion, dielectric constant and index of refraction is found. The pyroelectric, electrostrictive, electrooptic and non-linear-optical effects are of only mediocre magnitude except the electrostrictive constant d₂₁₁ which surmounts the longitudinal electrostrictive constant d₁₁₁ of alpha-quartz by a factor three.     

Single crystal growth of CaMg2(SO4)3 via solid‐ / gas‐phase reactions and its Nasicon‐related crystal structure

Crystals of the double sulfate CaMg₂(SO₄)₃ have been obtained by solid‐state reactions of stoichiometric amounts of anhydrous CaSO₄ and MgSO₄ in sealed and evacuated silica tubes with chlorine gas as mineraliser. The crystal structure was determined from single crystal X‐ray diffractometer data [P 6₃/m, Z = 2, a = 8.3072(4), c = 7.3057(8) Å, R [F² > 2σ (F²)] = 0.0317, wR (F² all) = 0.0785, 476 structure factors, 33 variable parameters] and consists of distorted [CaO₆] octahedra (3 symmetry), [MgO₆] octahedra (3 symmetry) and SO₄ tetrahedra (m symmetry) as single building units. The structure is made up of ¹_∞[CaO_6/2] chains of face‐sharing [CaO₆] octahedra that extend parallel to [001], alternating with columns of face‐sharing [MgO_3/1O_3/2]₂ dimers. Both types of chains are linked via corner‐sharing with SO₄ tetrahedra into a three‐dimensional framework structure. Although the compound crystallizes in a new structure type, it is topologically related to the NaZr₂(PO₄)₃ (Nasicon) structure, and a comparative discussion between both structural arrangements is given. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure and electrochemical property of one‐dimensional complex: [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]2[Cu(mnt)2]

One metalorganic complex [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]₂[Cu(mnt)₂] (mnt = maleonitriledithiolate) has been obtained by the reaction of dicyclohexyl‐18‐crown‐6 with K₂mnt and CuCl₂·2H₂O. The title complex has been characterized by elementary analysis, FT‐IR, UV‐Vis spectroscopy and x‐ray single crystal diffraction. The title complex crystallizes in the triclinic space group P1 with crystallographic data: a = 10.870(6) Å, b = 11.536(6) Å, c = 12.904(7) Å, α = 101.541(10)°, β = 110.573(9)°, γ = 99.441(9)°, V = 1435.2(13) ų, Z = 1, D_calcd = 1.350 g/cm³, F(000) = 615, R₁ = 0.0641, wR₂ = 0.1475. It displays one‐dimensional chain‐like structure formed by [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]⁺ complex cations and [Cu(mnt)₂]^2‐ complex anions through N‐K‐N interactions. Its electrochemical behavior has also been studied by the cyclic voltammetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structures and spectroscopic characterization of chiral and racemic 4‐phenyl‐1,3‐oxazolidin‐2‐one

Crystal structures of (R)‐ and (rac)‐4‐phenyl‐1,3‐oxazolidin‐2‐one (4‐POO) have been determined by X‐ray diffraction and characterized by the solid state ¹³C NMR and IR spectra. Molecular geometries and intermolecular interactions in (R)‐ and (rac)‐4‐POO crystals are very similar to each other; 4‐POO molecules are linked via the N‐H…O intermolecular hydrogen bonds to form the chained structure. Chemical shifts of the solid state ¹³C NMR spectra are very similar to each other, whereas the ¹H spin‐lattice relaxation times (T_1H) value for (R)‐4‐POO is five times as large as that for (rac)‐4‐POO, reflecting the more restricted mobility of the (R)‐4‐POO chain. Although both crystals contain an unique molecule in the asymmetric unit, a doublet feature is observed for the C=O stretching mode in the IR spectra of (R)‐ and (rac)‐4‐POO crystals. The frequency gap of the C=O bands are correlated with the strength of the dipole‐dipole interactions between the neighboring C=O groups. © 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Crystal and molecular structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione

The crystal structure of 1‐allyl‐5‐(4‐methylbenzoyl)‐4‐(4‐methylphenyl)pyrimidine‐2(1H)‐thione (C₂₂H₂₀N₂OS) has been determined from three dimensional single crystal X‐ray diffraction data. The title compound crystallizes in the monoclinic space group P 2₁/c, with a = 10.6674(13), b = 10.1077(7), c = 17.9467(19) Å, β = 98.460(9)°, V = 1914.0(3) ų, D_calc = 1.251 g cm^–3, Z = 4. In the title compound, the allyl group shows positional disorder. Molecules are linked by C‐H···O, C‐H···N and C‐H···S intermolecular interactions forming two‐dimensional network. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solvothermal syntheses and crystal structures of two 4‐heterocyclic acylpyrazolone complexes

Many explorations of transition metal (M)‐L system under solvothermal condition, have led to the syntheses of two new 4‐heterocyclic acylpyrazolone complexes [Co(L)₂(CH₃OH)₂] (HL = 1‐phenyl‐3‐methyl‐4‐(2‐furoyl)‐5‐pyrazolone) ( 1 ) and [Cr(L)₃] ( 2 ). Single‐crystal X‐ray analyses reveal that crystal structures of compound 1 and 2 are respectively orthorhombic, Pbca, a = 15.0378(6) Å, b = 9.8405(4) Å, c = 20.7321(8) Å, V = 3067.9(2) ų, Z = 8 and triclinic, P‐1, a = 10.7966(18) Å, b = 13.023(2) Å, c = 15.520(3) Å, α = 73.011(4)°, β = 84.884(4)°, γ = 70.267(4)°, V = 1964.3(6) ų, Z = 2. Complex 1 has a two‐dimensional (2D) network structure that is formed by O–H···N H‐bonding interactions. Complex 2 makes a one‐dimensional (1D) zigzag chain structure by intermolecular π···π interactions, which is further interlinked via C–H···N H‐bonding interactions to generate a 2D sheet, and then a three‐dimensional (3D) supramolecular network structure is further linked by intermolecular C–H···π interactions. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical properties of pure and metal ions doped ammonium sulfate single crystals

A study of the optical properties of pure‐and some metal ions doped ammonium sulfate crystals (AS) were made. Optical constants of AS crystals were calculated at room temperature. The optical absorption coefficient (α ) was analyzed and interpreted to be in the allowed direct transition. The introduction of Rb⁺ or Cs⁺ ions gives rise to an intense charge transfer band with a maximum at λ= 310 nm in the optical spectrum. In case of Cr³⁺ ‐doping, the absorption shows a shoulder just before the onset band to band transition. The values of the allowed direct energy gap E_g for undoped and doped crystals were calculated. It was found that E_g values were decreased with metal ions doping. The refractive index, the extinction coefficient and both the real and imaginary parts of the dielectric permittivity were calculated as a function of photon energy. The validity of Cauchy‐Sellimeier equation was checked in the wavelength range 4.9 ‐ 5.6 eV and its parameters were calculated. Applying the Single‐Effective‐Oscillator model, the moments of ε (E ) could be estimated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Syntheses and X‐Ray crystal structures of aminated 4,4'‐Bi‐1,2,4‐triazole salts

3‐Amino‐4,4'‐bi‐1,2,4‐triazole hydrochlorate and 3,3'‐diamino‐4,4'‐bi‐1,2,4‐triazole ditosylate were obtained with the reduction of 3,3',5,5'‐tetraazide‐4,4'‐bi‐1,2,4‐triazole (TABT) by (Ph)₃P/H₂O and the followed salt forming reaction with concentrated HCl and aqueous TsOH, respectively. Their structures were characterized with elemental analyses, IR, MS, ¹H and ¹³C NMR spectra. The single crystals were cultivated and determined with X‐ray diffraction, test results reveal that H⁺ combines with electron‐rich N atom in triazole ring to form ionic salts, two N,N‐linked triazoles are almost perpendicular to each other due to lower steric hindrance. The aromatic π…π stacking interactions and hydrogen bonds between molecules are observed. These two novel salts and their derivatives may be applied in coordination chemistry, medicinal chemistry and energetic materials.