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.

Li2 MTeO6 (M=Ti, Sn): Mid-Infrared Nonlinear Optical Crystal with Strong Second Harmonic Generation Response and Wide Transparency Range

Oxide crystals have been widely used in nonlinear optics (NLO) in the ultraviolet-visible and near-infrared regions. Most traditional oxide crystals are restricted to the mid-infrared region due to their narrow transmission window. Hence, attempting to extend infrared cutoff wavelength of oxides has attracted much attention. Herein, we report two new tellurates Li₂ TiTeO₆ (LTT) and Li₂ SnTeO₆ (LST) with broad transparent regions of 0.38-6.72 and 0.38-6.86 μm, respectively, as excellent candidates for mid-infrared NLO applications. Both LTT and LST crystallize in the orthorhombic space group Pnn2. The LTT crystal exhibits intense powder second-order generation efficiency (26×KDP) under the fundamental wavelength of 1064 nm. First-principles calculations and dipole moments were used to illustrate the results of the powder second-harmonic generations based on the crystal structures. Our results provide a novel oxide NLO crystal with a strong SHG and wide transparency range. They also pave a way for the design of new oxide mid-IR NLO crystals.

Pressure-dependent modifications in the optical and electronic properties of Fe(IO3)3: the role of Fe 3d and I 5p lone–pair electrons

The electronic and transport properties of Fe(IO3)3 have been characterized under compression. A nice correlation of bandgaps of iodates to orbital configuration is proposed giving an explanation for the 2.1 eV bandgap of Fe(IO3)3.

Structural Complexity and Magnetic Orderings in a Large Family of 3d-4f Heterobimetallic Sulfates

The synthesis of a large family of heterobimetallic lanthanide copper sulfates was realized via stoichiometric hydrothermal reactions among Ln₂O₃, CuO, and H₂SO₄, giving rise to four distinct phases, namely Ln₂Cu(SO₄)₂(OH)₄ (Ln = Sm-Ho) (LnCuSO₄-1), Ln₄Cu(SO₄)₂(OH)₁₀ (Ln = Tm-Lu) (LnCuSO₄-2), LnCu(SO₄)(OH)₃ (Ln = Nd-Gd, except Pm) (LnCuSO₄-3), and LnCu(SO₄)(OH)₃ (Ln = Dy-Lu) (LnCuSO₄-4), with completely different topologies. The passage from LnCuSO₄-1 and LnCuSO₄-3 to LnCuSO₄-2 and LnCuSO₄-4 across the 4f series, respectively, can be ascribed to the effect of lanthanide contraction, which progressively induces shrinking of the Ln-O distance, reduction in the Ln coordination number, and eventually structural transitions. The incorporation of identical 3d-4f metal ions into different spin-lattices, in conjunction with substitution of diverse Ln³⁺ cations within the same spin-lattice, gives rise to tunable magnetic properties varying from ferromagnetic ordering in GdCuSO₄-3 and HoCuSO₄-4 to antiferromagnetic ordering in YbCuSO₄-4, and to paramagnetic correlations found in GdCuSO₄-1 and YbCuSO₄-2.

Investigation into the optimized growth, anisotropic properties and theoretical calculations of the polar material Cs2TeW3O12

Bulk single crystals of Cs₂TeW₃O₁₂ were grown successfully by a modified TSSG method and physical properties were systematically investigated.

Excellent Infrared Nonlinear Optical Crystals BaMO(IO₃)₅ (M = V, Ta) Predicted by First Principle Calculations

Two nonlinear optical crystals, BaVO(IO₃)₅ and BaTaO(IO₃)₅, are designed by substituting Nb with V and Ta, respectively, in BaNbO(IO₃)₅, which is itself a recently synthesized infrared nonlinear optical (NLO) material. The designs of BaVO(IO₃)₅ and BaTaO(IO₃)₅ from BaNbO(IO₃)₅ are based on the following motivation: BaVO(IO₃)₅ should have a larger second-harmonic generation (SHG) coefficient than BaNbO(IO₃)₅, as V will result in a stronger second-order Jahn-Teller effect than Nb due to its smaller ion radius; at the same time, BaTaO(IO₃)₅ should have a larger laser-damage threshold, due to the fact that Ta has a smaller electronegativity leading to a greater band-gap. Established on reliable first-principle calculations, it is demonstrated that BaVO(IO₃)₅ has a much larger SHG coefficient than BaNbO(IO₃)₅ (23.42 × 10⁻⁹ vs. 18.66 × 10⁻⁹ esu); and BaTaO(IO₃)₅ has a significantly greater band-gap than BaNbO(IO₃)₅ (4.20 vs. 3.55 eV). Meanwhile, the absorption spectra and birefringences of both BaVO(IO₃)₅ and BaTaO(IO₃)₅ are acceptable for practice, suggesting that these two crystals can both be expected to be excellent infrared NLO materials.

Metal-organic frameworks as competitive materials for non-linear optics

The last five years have witnessed a huge breakthrough in the creation and the study of the properties of a new class of compounds - metamaterials. The next stage of this technological revolution will be the development of active, controllable, and non-linear metamaterials, surpassing natural media as platforms for optical data processing and quantum information applications. However, scientists are constantly faced with the need to find new methods that can ensure the formation of quantum and non-linear metamaterials with higher resolution. One such method of producing metamaterials in the future, which will provide scalability and availability, is chemical synthesis. Meanwhile, the chemical synthesis of organized 3D structures with a period of a few nanometers and a size of up to a few millimeters is not an easy task and is yet to be resolved. The most promising avenue seems to be the use of highly porous structures based on metal-organic frameworks that have demonstrated their unique properties in the field of non-linear optics (NLO) over the past three years. Thus, the aim of this review is to examine current progress and the possibilities of using metal-organic frameworks in the field of non-linear optics as chemically obtained metamaterials of the future. The review begins by presenting the theoretical principles of physical phenomena represented by mathematical descriptions for clarity. Major attention is paid to the second harmonic generation (SHG) effect. In this section we compare inorganic single crystals, which are most commonly used to study the effect in question, to organic materials, which also possess the required properties. Based on these data, we present a rationale for the possibility of studying the non-linear optical properties of metal-organic structures as well as describing the use of synthetic approaches and the difficulties associated with them. The second part of the review explicitly acquaints the reader with a new class of materials which successfully combines the positive properties of organic and inorganic materials. Using recently synthesized metal-organic frameworks and coordination polymers in the field of non-linear optics as an example, we consider synthetic approaches used for obtaining materials with desired properties and the factors to be considered in this case. Finally, probable trends towards improving the quality of the synthesized materials with regards to their further use in the field of non-linear optical effects are described.

Th(VO3)2(SeO3) and Ln(VO3)2(IO3) (Ln = Ce, Pr, Nd, Sm, and Eu): unusual cases of aliovalent substitution

Six isotypic compounds with rather extreme examples of aliovalent substitution (Th^IVvs. Ln^III; SeO₃²⁻vs. IO₃⁻) have been synthesized.

Dimensionality variations in new zirconium iodates: hydrothermal syntheses, structural determination, and characterization of BaZr(IO3)6 and K2Zr(IO3)6

While BaZr(IO₃)₆ reveals a unidimensional band structure, K₂Zr(IO₃)₆ exhibits a zero-dimensional molecular geometry. The dimensionality variations are attributable to the flexible coordination numbers of Zr⁴⁺ cations with large ionic radii as well as the number of counter cations.

PbPt(IO3)6(H2O): a new polar material with two types of stereoactive lone-pairs and a very large SHG response

A new polar material containing two types of stereoactive lone-pairs has been synthesized. The unique parallel alignment of the stereoactive lone-pairs on Pb(2+) cations and the synergistic effect of two types of stereoactive lone-pairs on I(5+) and Pb(2+) cations make it exhibit a very large second-harmonic generation response of about 8 × KDP (KH(2)PO(4)).