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.

Ag3I[(MoO3)2(IO3)2]: a new polar material synthesized from the structural modulation of molybdenyl iodate architectures by polarizable cation (Ag+) and anion (I−)

A new noncentrosymmetric compound Ag₃I[(MoO₃)₂(IO₃)₂] has been hydrothermally synthesized and characterized.

Role of the metal cation types around VO4 groups on the nonlinear optical behavior of materials: experimental and theoretical analysis

We combined experimental and theoretical studies of β_II-Li₃VO₄, KCd₄(VO₄)₃ and Ca₃(VO₄)₂ crystals, which turns out that the metal cation types and coordination around VO₄ groups, the distorted and parallel oriented VO₄ tetrahedron, could produce the large SHG coefficient.

Three new phosphates with isolated P2O7units: noncentrosymmetric Cs2Ba3(P2O7)2and centrosymmetric Cs2BaP2O7and LiCsBaP2O7

Three new phosphates, a noncentrosymmetric (NCS) Cs₂Ba₃(P₂O₇)₂and centrosymmetric (CS) Cs₂BaP₂O₇and LiCsBaP₂O₇, have been synthesized from high-temperature solutions for the first time.

Macroscopic polarity control with alkali metal cation size and coordination environment in a series of tin iodates

The IO₃ groups in Na₂Sn(IO₃)₆ are aligned in a parallel manner attributed to the six-coordinate Na⁺ cation, whereas the IO₃ polyhedra in Cs₂Sn(IO₃)₆ rotate with respect to Sn⁴⁺ due to the nine-coordinate Cs⁺ cation.

Role of acentric displacements on the crystal structure and second-harmonic generating properties of RbPbCO3F and CsPbCO3F

Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet-visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6m2 (crystal class 6m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × α-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even-odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb(2+). The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates.

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.