Rational Design of the Alkali Metal Sn-Based Mixed Halides with Large Birefringence and Wide Transparent Range.

Birefringent materials are widely used in various advanced optical systems, owing to their vital role in creating and controlling polarized light. Currently, Sn-based compounds containing stereochemically active lone-pair (SCALP) cations are extensively investigated and considered as one class of promising birefringent materials. To solve the problem of relatively narrow bandgap of Sn-based compounds, alkali metals and multiple halogens are introduced to widen the bandgap during the research.

MnCaTaO-A Magnetically Ordered Polar Phase Prepared via Cation Exchange.

Reaction between the pseudo-Ruddlesden-Popper phase LiCaTaO and MnCl at 375 °C yields MnCaTaO, a paramagnetic polar phase (space group 2), which adopts an / distorted, layered perovskite structure. Magnetization and neutron diffraction data show that MnCaTaO adopts an antiferromagnetically ordered state below = 56 K and exhibits large lattice parameter anomalies and a transient increase in its polar distortion mode at = 50 K. However, in contrast to the related phase MnSrTaO, MnCaTaO shows no strong signature of weak ferromagnetism and thus shows no signs of magnetoelectric coupling.

Beyond π-π Stacking: Understanding Inversion Symmetry Breaking in Crystalline Racemates.

The design of noncentrosymmetric (NCS) solid state materials, specifically how to break inversion symmetry between enantiomers, has intrigued chemists, physicists, and materials scientists for many years. Because the chemical complexity of molecular racemic building units is so varied, targeting these materials is poorly understood. Previously, three isostructural racemic compounds with a formula of [Cu(HO)(bpy)][MF]·2HO (bpy = 2,2'=bipyridine; M = Ti, Zr, Hf) were shown to crystallize in the NCS space group 2, of polar, achiral crystal class 2.

Crystal Structures and Property Measurements of Rare Earth Magnesium Thiosilicates Synthesized via Flux Crystal Growth Utilizing the Boron Chalcogen Mixture (BCM) Method.

Nine new rare earth magnesium-containing thiosilicates of the formula REMgSiS (Ln = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) were synthesized in an alkali halide flux using the boron chalcogen mixture (BCM) method. Crystals of high quality were produced, and their structures were determined by single-crystal X-ray diffraction. The compounds crystallize in the hexagonal crystal system in the 6 space group.

Polarizable Anionic Sublattices Can Screen Molecular Dipoles in Noncentrosymmetric Inorganic-Organic Hybrids.

We report the growth and photophysical characterization of two polar hybrid lead halide phases, methylenedianiline lead iodide and bromide, (MDA)PbI and (MDA)PbBr, respectively. The phases crystallize in noncentrosymmetric space group 2, which produces a highly oriented molecular dipole moment that gives rise to second harmonic generation (SHG) upon excitation at 1064 nm. While both compositions are isostructural, the size dependence of the SHG signal suggests that the bromide exhibits a stronger phase-matching response whereas the iodide exhibits a significantly weaker non-phase-matching signal.

NaRb(BO(OH))(BO) Featuring Noncentrosymmetry, Chirality, and the Linear Anionic Group BO.

Noncentrosymmetric (NCS) structures are of particular interest owing to their symmetry-dependent physical properties, e.g., pyroelectricity, ferroelectricity, piezoelectricity, and nonlinear optical (NLO) behavior.

Noncentrosymmetric γCsIO Obtained from IO Polyhedral Rearrangements in the Centrosymmetric βPhase.

We report the synthesis and optical properties of noncentrosymmetric (NCS) γCsIO that was obtained through IO polyhedral rearrangements from centrosymmetric (CS) β-CsIO. Trifluoroacetic acid (TFA) acts as a structure-directing agent and plays a key role in the synthesis. It is suggested that the function of TFA is to promote rearrangement reactions found in the organic synthesis of stereoisomers.

BiCoOF-A Polar, Ferrimagnetic Aurivillius Oxide-Fluoride.

Aurivillius oxides have been a research focus due to their ferroelectric properties, but by replacing oxide ions by fluoride, divalent magnetic cations can be introduced, giving Bi OF ( = Fe, Co, and Ni). Our combined experimental and computational study on BiCoOF indicates a low-temperature polar structure of 2 symmetry (analogous to ferroelectric BiWO) and a ferrimagnetic ground state. These results highlight the potential of Aurivillius oxide-fluorides for multiferroic properties.

Lanthanide thioborates, an emerging class of nonlinear optical materials, efficiently synthesized using the boron-chalcogen mixture method.

The Boron-Chalcogen Mixture method was used to obtain single crystals of the previously extremely difficult to synthesize lanthanide orthothioborates to investigate their structures and their structurally connected optical behavior, such as second harmonic generation. Using a combined halide and polychalcogenide flux, the BCM method yielded single crystals of LnBS (Ln = La, Ce, Pr, Nd), which are isostructural and crystallize in the non-centrosymmetric space group, 2. Second harmonic generation measurements confirmed the expectation that LaBS would exhibit a strong SHG response, measured at 1.

Oxide Ion Conductivity, Proton Conductivity, and Phase Transitions in Perovskite-Derived Ba Sr YGaO 0 ≤ ≤ 3 Materials.

We report the synthesis, structural characterization, and oxide ion and proton conductivities of the perovskite-related Ba Sr YGaO family. Single-phase samples are prepared for 0 ≤ ≤ 3 and show a complex structural evolution from 2/ to 2 space groups with an increase in . For 1.

Polarity and Ferromagnetism in Two-Dimensional Hybrid Copper Perovskites with Chlorinated Aromatic Spacers.

Two-dimensional (2D) organic-inorganic hybrid copper halide perovskites have drawn tremendous attention as promising multifunctional materials. Herein, by incorporating -, -, and -chlorine substitutions in the benzylamine structure, we first report the influence of positional isomerism on the crystal structures of chlorobenzylammonium copper(II) chloride perovskites ACuCl. 2D polar ferromagnets (3-ClbaH)CuCl and (4-ClbaH)CuCl (ClbaH = chlorobenzylammonium) are successfully obtained.

The crystal and defect structures of polar KBiNbO.

KBiNbO was prepared from RbBiNbO by a sequence of cation exchange reactions which first convert RbBiNbO to LiBiNbO, before KBiNbO is formed by a further K-for-Li cation exchange. A combination of neutron, synchrotron X-ray and electron diffraction data reveal that KBiNbO adopts a polar, layered, perovskite structure (space group 11) in which the BiNbO layers are stacked in a (0, ½, ) arrangement, with the K cations located in half of the available 10-coordinate interlayer cation sites. The inversion symmetry of the phase is broken by a large displacement of the Bi cations parallel to the -axis.

Perovskite-like KTiOF Exhibits (3 + 1)-Dimensional Commensurate Structure Induced by Octahedrally Coordinated Potassium Ions.

Elpasolite- and cryolite-type oxyfluorides can be regarded as superstructures of perovskite and exhibit structural diversity. While maintaining a similar structural topology with the prototype structures, changes in the size, electronegativity, and charge of cation and/or anion inevitably lead to structural evolution. Therefore, the nominal one-to-one relation suggested by a doubled formula of perovskite does not guarantee a simple 2-fold superstructure for many cases.

The influence of the 6s configuration of Bi on the structures of A'BiNbO (A' = Rb, Na, Li) layered perovskite oxides.

Solid state compounds which exhibit non-centrosymmetric crystal structures are of great interest due to the physical properties they can exhibit. The 'hybrid improper' mechanism - in which two non-polar distortion modes couple to, and stabilize, a further polar distortion mode, yielding an acentric crystal structure - offers opportunities to prepare a range of novel non-centrosymmetric solids, but examples of compounds exhibiting acentric crystal structures stabilized by this mechanism are still relatively rare. Here we describe a series of bismuth-containing layered perovskite oxide phases, RbBiNbO, LiBiNbO and NaBiNbO, which have structural frameworks compatible with hybrid-improper ferroelectricity, but also contain Bi cations which are often observed to stabilize acentric crystal structures due to their 6s electronic configurations.

Synthesis of Hydrated Ternary Lanthanide-Containing Chlorides Exhibiting X-ray Scintillation and Luminescence.

A series of new ternary lanthanide-based chlorides, CsEuCl(HO), CsLnCl(HO) (Ln = Gd or Ho), CsTbCl(HO)(HO), CsDyCl(HO), CsErCl(HO), and CsLnCl(HO) (Ln = Y, Lu, or Yb), were prepared as single crystals via a facile solution route. The compounds with compositions of CsLnCl(HO) (Ln = Gd or Ho) and CsLnCl(HO) (Ln = Y, Lu, or Yb) crystallize in a monoclinic crystal system in space groups 2 and 2/, respectively, whereas CsEuCl(HO), CsTbCl(HO)(HO), and CsErCl(HO) crystallize in orthorhombic space groups , , and 222, respectively. CsDyCl(HO) crystallizes with triclinic symmetry in space group 1̅.

Directed synthesis of a hybrid improper magnetoelectric multiferroic material.

Preparing materials which simultaneously exhibit spontaneous magnetic and electrical polarisations is challenging as the electronic features which are typically used to stabilise each of these two polarisations in materials are contradictory. Here we show that by performing low-temperature cation-exchange reactions on a hybrid improper ferroelectric material, LiSrTaO, which adopts a polar structure due to a cooperative tilting of its constituent TaO octahedra rather than an electronically driven atom displacement, a paramagnetic polar phase, MnSrTaO, can be prepared. On cooling below 43 K the Mn centres in MnSrTaO adopt a canted antiferromagnetic state, with a small spontaneous magnetic moment.

AgBi(SO)(IO): aliovalent substitution induces structure dimensional upgrade and second harmonic generation enhancement.

A new 3D noncentrosymmetric mixed-metal sulfate iodate, AgBi(SO)(IO), has been designed based on a 2D iodate of AgBi(IO)via the aliovalent substitution of [IO] groups by [SO] groups. Enhancement of the second harmonic generation response (3.0 × KDP to 3.

Interplay between Oxo and Fluoro in Vanadium Oxyfluorides for Centrosymmetric and Non-Centrosymmetric Structure Formation.

Herein, we report the syntheses of two lithium-vanadium oxide-fluoride compounds crystallized from the same reaction mixture through a time variation experiment. A low temperature hydrothermal route employing a viscous paste of VO, oxalic acid, LiF, and HF allowed the crystallization of one metastable phase initially, LiVO(HO)F⋅2HO (), which on prolonged heating transforms to a chemically similar yet structurally different phase, LiVOF (). Compound crystallizes in centrosymmetric space group, 2/ with = 6.

Tuning between Proper and Hybrid-Improper Mechanisms for Polar Behavior in Cs TiNbO Dion-Jacobson Phases.

The Dion-Jacobson (DJ) family of perovskite-related materials have recently attracted interest due to their polar structures and properties, resulting from hybrid-improper mechanisms for ferroelectricity in = 2 systems and from proper mechanisms in = 3 CsBiTiNbO. We report here a combined experimental and computational study on analogous = 3 Cs TiNbO ( = La, Nd) materials. Density functional theory calculations reveal the shallow energy landscape in these systems and give an understanding of the competing structural models suggested by neutron and electron diffraction studies.