Nonlinear optical crystal BiAlGa2(BO3)4

The new nonlinear optical crystals BiAlGa₂(BO₃)₄ have been grown by spontaneous crystallization with molten flux based on a Bi₂O₃–B₂O₃ solvent. From single crystal X-ray diffraction measurement, BiAlGa₂(BO₃)₄ has been found to crystallize in the trigonal huntite structure type, space group R32, with cell dimensions a = 9.4433(9) and c = 7.4130(10) Å. The diffuse reflectance spectrum on a powder sample indicated that the short-wavelength absorption edge of BiAlGa₂(BO₃)₄ extends to approximately 271 nm. Second-harmonic generation (SHG) on powder samples has been measured using Kurtz and Perry technique, which indicated that BiAlGa₂(BO₃)₄ is a phase-matchable material, and its SHG coefficient is measured to be four times as large as that of KDP.     

Non-centrosymmetric sodium borate: Crystal growth,characterization and properties on Na2B4O12H10

In this study, both solvent evaporation and hydrothermal methods were employed to grow hydrated sodium borate crystals using NaOH and H₃BO₃ as reagents, and transparent and colorless single-crystals were successfully obtained with sizes up to 12 × 6 × 6 mm³ and 6 × 5 × 4 mm³, respectively. The structure is determined by single-crystal X-ray diffraction techniques. The title compound crystallizes in the trigonal space group R32, with a = 11.1042(16) Å, b = 11.1042(16) Å, c = 21.131(4) Å, Z = 9 and R₁ = 0.0322, wR₂ = 0.0840. Infrared and transmission spectra are presented for the reported material. The powder second-harmonic generation (SHG) intensity measured by the Kurtz-Perry method indicates that the SHG effect of Na₂B₄O₁₂H₁₀ is about one-third times that of KH₂PO₄ (KDP).     

Synthesis and characterization of second-order nonlinear optical polyurethane with high thermal stability

A second-order nonlinear optical polyurethane was formed with an X-type multi-dimensional charge-transfer (CT) chromophore (DNPIPDHPI) and 3,3^′-dimethoxy-4,4^′-diphenyl diisocyanate. Simultaneous poling and polymerization and in situ second harmonic generation (SHG) measurement technique was carried on to evaluate the thermal stability of the poling induced orientation. The SHG signal of the poled polymer film was not decay below 150 °C and remains 90% of relative d₃₃ value at 200 °C, which is better than the results reported in literature. Comparison of thermal stability indicates that the X-type chromophores possess better property in controlling the decay of the SHG activity than classic chromophores.     

Algebraic symmetry and determination of the “imaginary” crystal field parameters from optical spectra of fn-ions. Hexagonal and trigonal symmetry

Algebraic symmetry of the characteristic equation of the crystal field hamiltonian Ĥ_CF for hexagonal (C₆, C_3h, C_6h) and trigonal (C₃, S₆) symmetry is considered. Explicit dependence of the coefficients a_i of the characteristic equation on the CF parameters is derived by ALTRAN. Magnitudes, signs and/or relative signs of the CF parameters which can be determined from fitting the optical spectra of fⁿ-ions at sites of the above symmetry are established. The algebraic results derived here can facilitate the fitting procedures for any hexagonal and trigonal symmetry. The relevant literature is extensively surveyed. The approach C (complete) to fitting the optical spectra, which yields ambiguous and unreliable results in general, has not been employed to hexagonal (C₆, C_3h, C_6h) symmetry. Some misinterpretations on the approach R (reduced) and A (approximated), which merge for this symmetry, are clarified. Crystal field analysis has been carried out for trigonal (C₃, S₆) symmetry in but a few cases only. The survey has revealed one case of the inappropriate C used for Eu³⁺ in the trigonal (C₃) Eu(DBM)₃ · H₂O system.     

Synthesis, crystal structure and nonlinear optical property of Rb3V5O14

The new nonlinear optical crystal Rb₃V₅O₁₄ has been synthesized by solid state reaction and characterized by single-crystal X-ray diffraction, IR and thermogravimetric analysis. The crystal Rb₃V₅O₁₄ crystallizes in the trigonal system with space P31m (No. 157), a=b=8.7134(12) Å, c=5.2807(11) Å and α=90°, β=90°, γ=120°, Z=1, ρ=3.516 g/cm³. It is a layered structure that is very flat and strongly parallel to c. The V₅O₁₄ layer structure consists of corner-linked square and triangular pyramids. The layers are separated by Rb⁺ ions, which fit equally well on the V₅O₁₄ layer. The Kurtz powder SHG measurement, using 1064 nm radiation, showed that the second-harmonic generation efficiency of Rb₃V₅O₁₄ is about two times that of KDP.     

Rational Design of the Metal-Free KBe2BO3F2⋅(KBBF) Family Member C(NH2)3SO3F with Ultraviolet Optical Nonlinearity

The first fluorosulfonic ultraviolet (UV) nonlinear optical (NLO) material, C(NH₂)₃SO₃F, is rationally designed by taking KBe₂BO₃F₂ (KBBF) as the parent compound. C(NH₂)₃SO₃F features similar topological layers as KBBF by replacing inorganic (BO₃)³⁻ with organic C(NH₂)₃⁺ trigonal units and BeO₃F with SO₃F⁻ tetrahedra. Therefore, C(NH₂)₃SO₃F is a metal-free UV NLO crystal. Benefiting from the coplanar configuration of the C(NH₂)₃⁺ cationic groups, it possesses a large SHG response of 5×KDP and moderate birefringence of 0.133@1064 nm. Besides, it has a short UV cutoff edge of 200 nm. The calculated results reveal the shortest SHG phase-matching wavelengths can reach 200 nm. These findings highlight the exploration of metal-free compounds as nontoxic and low-cost UV NLO materials as a new research area.     

Rational Design of the Metal‐Free KBe2BO3F2⋅(KBBF) Family Member C(NH2)3SO3F with Ultraviolet Optical Nonlinearity

The first fluorosulfonic ultraviolet (UV) nonlinear optical (NLO) material, C(NH₂)₃SO₃F, is rationally designed by taking KBe₂BO₃F₂ (KBBF) as the parent compound. C(NH₂)₃SO₃F features similar topological layers as KBBF by replacing inorganic (BO₃)^3? with organic C(NH₂)₃⁺ trigonal units and BeO₃F with SO₃F^? tetrahedra. Therefore, C(NH₂)₃SO₃F is a metal‐free UV NLO crystal. Benefiting from the coplanar configuration of the C(NH₂)₃⁺ cationic groups, it possesses a large SHG response of 5×KDP and moderate birefringence of 0.133@1064 nm. Besides, it has a short UV cutoff edge of 200 nm. The calculated results reveal the shortest SHG phase‐matching wavelengths can reach 200 nm. These findings highlight the exploration of metal‐free compounds as nontoxic and low‐cost UV NLO materials as a new research area.     

Investigations of the optical spectra and EPR g factors for the tetragonal Cu2+ centers in trigonal ZnCO3 crystal

Two distinctive theoretical methods, the complete diagonalization (of energy matrix) method (CDM) and the perturbation theory method (PTM), are employed to calculate the optical band positions and EPR g factors g_//, g_⊥ for the tetragonal Cu²⁺ centers in trigonal ZnCO₃ crystal. The results from the two methods coincide and are also in good agreement with the experimental values. So both the CDM and PTM are adequate for the investigations of optical and EPR data for d⁹ ions in crystals. The tetragonal distortion due to the static Jahn–Teller effect for the tetragonal Cu²⁺ centers in trigonal Zn²⁺ site of ZnCO₃ is also acquired from the calculations. The results are discussed.     

Lead-strontium borate halides with hilgardite-type structure and their SHG properties

Lead-containing members of the hilgardite family of borate halides, M₂B₅O₉X (M=Ca, Sr, Ba, Pb; X=Cl, Br) exhibit an abnormally large nonlinear optical response. In order to establish any underlying crystal-chemical rationale for this we have carried out detailed crystallographic characterisations of the representative members of this series, Sr₂B₅O₉Cl and Pb₂B₅O₉Cl, using powder neutron diffraction. Both adopt the orthorhombic hilgardite structure type, in space group Pnn2. The full solid solution range Pb_2−xSr_xB₅O₉Cl has also been prepared, and studied by X-ray Rietveld and second harmonic generation (SHG) measurements. The SHG response shows a linear decrease with increasing x, whereas the unit cell shows an increasing orthorhombic distortion. However, the crystallographic results suggest no significant or systematic changes in the nature of the borate sublattice between Sr₂B₅O₉Cl and Pb₂B₅O₉Cl. We conclude that the enhanced SHG response in Pb-containing hilgardites is due predominantly to the presence of the polarizable nature of Pb²⁺, in particular the presence of a stereochemically active lone pair.     

The crystal structure of the 2:5 phase in the K2OZrO2 system: K4Zr5O12, a compound with octahedral and trigonal prismatic zirconium(IV) coordination

K₄Zr₅O₁₂ crystallizes in the trigonal system with unit-cell dimensions a = 5.821(2) Å, c = 10.437(3) Å, and space group $\text{P}\text{3}\text{m1}$. The structure was solved by Patterson and Fourier techniques. the 386 unique reflections measured by counter techniques were reduced to 334 with I ? 3σ (I); these were used in full-matrix least-squares refinement of the model to a conventional R of 0.0196 (ωR = 0.0228). K₄Zr₅O₁₂ has a structure that may be described as consisting of perovskite-like layers (potassium ions are cube octahedrally coordinated) with sheets of hexagonal rings of edge-shared trigonal prismatically coordinated zirconium(IV) ions inserted between every third and fourth layer of the perovskite-like structure. The trigonal prisms are face shared to octahedra above and below alternately to form cavities that are occupied by pairs of potassium ions in ninefold coordination.     

Effects of fluorine atoms on the optical nonlinear response of stilbene derivatives

The effect of fluorine atoms on the second-order optical nonlinear response of 4-nitro-4′-methoxy-trans-stilbene and polyene derivatives containing up to three double bonds (n=1, 2, 3) has been investigated within a semiempirical context (PM3 Hamiltonian). Experimental data reported in literature indicate a β_vec(SHG) value of 34, 47 and 76 (×10⁻³⁰ esu) for n=1, 2, 3, respectively, at 0.65 eV in CHCl₃ solutions. Our calculations show that fluorinating the nitrophenyl group the β_vec(SHG) is doubled. Further increase in the second-order nonlinear response can be obtained fluorinating the CC bond linkers between the aromatic moieties.Besides, the effect of different donor-acceptor pairs has been studied and the results interpreted in the two-state model context.Some results concerning the third-harmonic generation (THG), γ (THG), are presented, and a possible interpretation proposed.     

Phase diagram of SrO-InO1.5-CoOx and a new compound Sr3In0.9Co1.1O6

Sr₃In_0.9Co_1.1O₆, isostructural to Ca₃Co₂O₆, is revealed by the study of the phase relations in the system SrO-InO_1.5-CoO_x (1000 °C). The structure of Sr₃In_0.9Co_1.1O₆ is refined by the combination of powder X-ray and neutron diffraction. Sr₃In_0.9Co_1.1O₆ crystallizes in a trigonal lattice with the cell parameters a=b=9.59438(3) Å, c=11.02172(4) Å with the space group R-3c. Its structure possesses 1D (In/Co)O₃ chains running along the c-axis constructed by alternating face-sharing CoO₆ octahedra and (In_0.9Co_0.1)O₆ trigonal prisms. The co-occupation of In³⁺ and Co³⁺ at the trigonal prismatic site is evidenced by elementary analysis and determined by the structure refinement. Sr₃In_0.9Co_1.1O₆ is paramagnetic, and the susceptibility is consistent with the occupation of Co³⁺ at 10% of the trigonal prismatic positions in a high spin state (HS, S=2). The HS Co³⁺ is well separated by diamagnetic CoO₆ octahedra and InO₆ trigonal prisms and shows a g factor of 2.0 in the magnetic measurements.     

Temperature resolved second harmonic generation to probe the structural purity of m-hydroxybenzoic acid

We report the use of second harmonic generation (SHG) and temperature resolved second harmonic generation (TR-SHG) for in situ probing and monitoring the structural purification of m-hydroxybenzoic acid (MHBA). Pure and mixtures of the two polymorphic forms of MHBA (metastable Pna2₁ and stable P2₁/c) and commercial MHBA were analysed by: DSC, XRPD and SHG. Results obtained with these three techniques are compared and demonstrate for that particular component, the high sensitivity and accuracy of SHG in assessing the polymorphic purity of MHBA. The SHG detection threshold for the metastable polymorph is circa 2 ppm and is several orders of magnitude better than the sensitivity of XRPD (1 wt%) and DSC (only 17 wt%). The proportion of the metastable phase in the commercial MHBA was evaluated to 1 wt% by SHG. Results of TR-SHG measurements performed on commercial MHBA at 5 K min^?1 heating rate show that TR-SHG is a good technique for an in situ monitoring of the structural purity. The present study clearly demonstrates that SHG and TR-SHG are relevant and accurate techniques for probing the structural purity and for the monitoring of solid–solid phase transitions provided one of the two varieties crystallizes in a non-centrosymmetric space group.     

Second-harmonic properties of dendritic polymers skeleton-constructed with azobenzene moiety used for nonlinear optical materials

A series of dendrons and dendrimers skeleton-constructed with azobenzene moiety were synthesized and doped in a high T_g polycarbonate (PC) as a host for nonlinear optical (NLO) materials. The optimal loading density and poling conditions were investigated using UV-vis spectral and second-harmonic generation (SHG) measurements. The results showed that the dendrons and dendrimers have good solubility in PC host, which increased with the generation increased. Moreover, the SHG measurements indicated that the dendrons possess higher nonlinearity than the dendrimers. The chromophores of lower generation dendrons were easier to orient along the poling electric field and gave a cone shape with the azobenzene branching units, which coherently contributed to the molecular hyperpolarizability and resulted in the higher SHG intensity. The temporal stability of the dendrons with 15% loading density was also investigated, and showed that the decaying in nonlinearity was slower for higher generation dendrons.     

Na4ReN3, das erste Alkalimetall‐Nitridorhenat(V)

Na₄ReN₃, the First Alkali Metal Nitridorhenate(V) Rhenium powder reacts in a mixture with NaNH₂ in autoclaves at 773 K to orange colored crystals embedded in a matrix of sodium metal. After extracting the sodium metal with liquid ammonia single crystals were seperated. The structure was solved by X‐ray single crystal methods and for the evaluation of the correct space group by optical SHG experiments: spacegroup Cc (No. 9), Z = 4, a = 10.903(2) Å, b = 6.022(1) Å, c = 8.944(2) Å, β = 115.57(3)°. The structure contains trigonal pyramidal anions ReN₃^4–, which are embedded in three‐dimensionally linked, fourfold capped cubes of 12 Na.     

Syntheses,characterization and nonlinear optical properties of sodium–scandium carbonate Na5Sc(CO3)4·2H2O

A novel nonlinear optical (NLO) material Na₅Sc(CO₃)₄·2H₂O has been synthesized under a subcritical hydrothermal condition. The structure is determined by single-crystal X-ray diffraction and further characterized by TG analyses and UV–vis–NIR diffuse reflectance spectrum. It crystallizes in the tetragonal space group P-421c, with a = b = 7.4622(6) Å, C = 11.5928(15) Å. The Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that Na₅Sc(CO₃)₄·2H₂O was a phase-matchable material, and its measured SHG coefficient was about 1.8 times as large as that of d₃₆ (KDP). The results from the UV–vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges of Na₅Sc(CO₃)₄·2H₂O is about 220 nm, suggesting that this crystal is a promising UV nonlinear optical (NLO) materials.     

K3V2O3F4(IO3)3: a high-performance SHG crystal containing both five and six-coordinated V5+ cations

The combination of d⁰ transition metal oxofluorides with iodate anions helps to synthesize polar crystals. Herein, a novel polar crystal, K₃V₂O₃F₄(IO₃)₃, which is the first metal vanadium iodate with two types of V⁵⁺-centered polyhedra (VO₄F₂ octahedron and VO₃F₂ trigonal bipyramid), has been prepared hydrothermally. It crystallizes in the polar space group of Cmc2₁ and its structure displays an unprecedented 0D [V₂O₃F₄(IO₃)₃]³⁻ anion, which is composed of Λ-shaped cis-[VO₂F₂(IO₃)₂]³⁻ and [VO₂F₂(IO₃)]²⁻ anions interconnected via the corner-sharing of one oxo anion. The synergy gained from the VO₄F₂, VO₃F₂ and IO₃ groups resulted in K₃V₂O₃F₄(IO₃)₃ exhibiting both a strong second-harmonic generation (SHG) response (1.3 × KTiOPO₄) under 2050 nm laser irradiation and a large birefringence (0.158 @ 2050 nm). This study provides a facile route for designing SHG materials by assembling various vanadium oxide-fluoride motifs and iodate anions into one compound.

K₃V₂O₃F₄(IO₃)₃, which is the first metal vanadium iodate containing two different V-centered polyhedra, exhibits a strong SHG effect of 1.3 × KTP and a large birefringence of 0.158 @ 2050 nm.     

The crystal structure of 3-R Nb1.06S2

The X-ray single crystal structure of 3-R Nb_1.06S₂ has been determined. The material crystallizes in the space group R_3m with a = 3.3285(4) and c = 17.910(4) Å when indexed on a hexagonal lattice. The structure was refined by full matrix least squares procedures to a final residual of R = 0.026 based on 79 observed (I > 3σ_I) reflections. The sulfurs form closest-packed layers with the majority of the metal in sheets of trigonal prismatic sites. A small portion of niobium was found to occupy octahedral sites, between the van der Waals gaps of the sulfur lattice. Niobium in the van der Waals region is trigonally distorted from octahedral symmetry, with niobium-sulfur distances of 2.234(8) and 2.577(11) Å, because of repulsion from niobium in adjacent trigonal prismatic layers.     

Hydrothermal preparation,structure and characterizations of noncentrosymmetric LiZnO(IO3)

A new lithium zinc iodate, LiZnO(IO₃), has been prepared by hydrothermal reactions at 200 °C. Single-crystal X-ray diffraction experiment revealed that the compound crystallizes in a noncentrosymmetric orthorhombic space group Ama2 with cell parameters: a = 6.3386(6) Å, b = 11.2613(11) Å, c = 4.6840(5) Å, Z = 4. In the structure, the basic building units are the distorted ZnO₆ octahedron, LiO₄ tetrahedron and the IO₃ group. These groups are linked together to form a three-dimensional structure by sharing the oxygen atoms. The DSC measurement demonstrates that the compound is stable up to 490 °C. Powder second-harmonic generation (SHG) test shows that the SHG effect is about 2 × KH₂PO₄.     

Synthesis, structure and physical properties of Ru ferrites: BaMRu5O11 (M=Li and Cu) and BaM′2Ru4O11 (M′=Mn, Fe and Co)

The synthesis, structure, and physical properties of five R-type Ru ferrites with chemical formula BaMRu₅O₁₁ (M=Li and Cu) and BaM′₂Ru₄O₁₁ (M′=Mn, Fe and Co) are reported. All the ferrites crystallize in space group P6₃/mmc and consist of layers of edge sharing octahedra interconnected by pairs of face sharing octahedra and isolated trigonal bipyramids. For M=Li and Cu, the ferrites are paramagnetic metals with the M atoms found on the trigonal bipyramid sites exclusively. For M′=Mn, Fe and Co, the ferrites are soft ferromagnetic metals. For M′=Mn, the Mn atoms are mixed randomly with Ru atoms on different sites. The magnetic structure for BaMn₂Ru₄O₁₁ is reported.