Ba4B8TeO19: A UV Nonlinear Optical Material

PbTeB4O9: a lead tellurium borate with unprecedented fundamental building block [B4O10] and large birefringence

Herein, the first lead tellurium borate, PbTeB4O9, with an unprecedented fundamental building block [B4O10] was successfully synthesized. The near-parallel alignment of [B4O10] groups and [TeO3] polyhedra resulted in a high birefringence (0.099@1064 nm). The structure-property relationship was discussed by using the first-principles calculations.

MM'B3O4F3 (M = K; M' = Na, K, Cs): Alkali-Metal Fluorooxoborates with ∞1[B3O4F3] Chains and Deep-Ultraviolet Cutoff Edges

Three mixed-alkali-metal fluorooxoborates, KNaB₃O₄F₃ (I), K₂B₃O₄F₃ (II), and KCsB₃O₄F₃ (III), were acquired in a closed system. I-III are isomorphic and adopt orthorhombic structures [Pbcn (No. 60)] with wavy parallelly arranged pseudolayers composed of _∞¹[B₃O₄F₃] chains, which exhibit slight differences in the arrangement modes of the fundamental building blocks. First-principles calculations illustrate that they all have moderate birefringence and large band gaps on the order of 7.0 eV, suggesting deep-ultraviolet (DUV) cutoff edges. In order to investigate the main source of the optical properties, the electronic structure and anisotropy of the response electron distribution were analyzed. Experimental characterizations for I confirm the structure and DUV transparence ability.

Lead Tellurite Crystals BaPbTe2O6 and PbVTeO5F with Large Nonlinear-/Linear-Optical Responses due to Active Lone Pairs and Distorted Octahedra

The exploration of nonlinear-/linear-optical crystal materials with high performance is an extremely difficult research project. Herein, the two new lead tellurite crystals BaPbTe₂O₆ and PbVTeO₅F were successfully obtained through a facile hydrothermal synthesis strategy. BaPbTe₂O₆ lies in the noncentrosymmetric (NCS) and chiral orthorhombic space group P2₁2₁2₁, featuring a unique _∞¹[PbTe₂O₆] chain consisting of the PbO₄ and TeO₃ building units, while PbVTeO₅F belonging to the centrosymmetric (CS) orthorhombic space group Pbca manifests a 2D layer made up of _∞¹[PbO₄F₂] chains and novel [V₂Te₂O₁₀F₂] clusters. Further, a systematic analysis of lead tellurites finds that the coordination geometries of the Pb atom exert a considerable influence on the connection modes of Pb-O and Te-O building units. BaPbTe₂O₆ shows a great second-harmonic-generation (SHG) effect of ∼5× the benchmark KH₂PO₄ (KDP) and a large optical birefringence of 0.086 at 590 ± 3 nm. PbVTeO₅F demonstrates a remarkably larger birefringence of 0.142 at 590 ± 3 nm, benefiting from the introduction of the VO₅F octahedral unit. Theoretical studies reveal that the large SHG and birefringence in BaPbTe₂O₆ can be attributed to TeO₃ and PbO₄ polyhedra with active lone pairs, while the remarkably enlarged birefringence in PbVTeO₅F is attributable to the highly distorted octahedral VO₅F. The functional orientations of active building units may offer a practical insight into the design of the desired optical functional materials.

Dependence of Luminous Performance on Eu3+ Site Occupation in SrIn2(P2O7)2: The Effect of the Local Environment

The photoluminescence behavior of luminescent materials with rare earth (RE) ions as a luminescence center not only depends on the element type and chemical valence of RE ions but also on their concentration and occupation in the matrix, sometimes including the interaction of the matrix and RE ions or between different RE ions. Herein, special SrIn₂(P₂O₇)₂ phosphate, assembled by monolayer [SrO₁₀]_∞ and bilayer [In₂P₄O₁₄]_∞ consisting of InO₆ units and P₂O₇ groups, was selected as the host material, and different cation positions (Sr and In) were substituted by Eu³⁺. The structure refinement in combination with Judd-Ofelt theory has shed light on the differences of the Eu³⁺ coordination environment in SrIn₂(P₂O₇)₂. The structural rigidity of the In³⁺ site is better than that of the Sr²⁺ site, making SrIn_1.92(P₂O₇)₂: Eu_0.08 superior in thermal stability. The average distance between adjacent Sr²⁺ ions is larger than that between adjacent In³⁺ ions, causing the higher quantum efficiency of Sr_0.9In₂(P₂O₇)₂: Eu_0.1. The present work demonstrates that the site occupation of Eu³⁺ has an important effect on its luminous performance. Importantly, the newly developed Eu³⁺-doped SrIn₂(P₂O₇)₂ phosphors, exhibiting outstanding luminous efficiency, favorable thermal stability, and excellent color purity, are promising red components of phosphor-based light-emitting diodes.

K2 Na3 [{B6 O10 (OH)}{B3 O4 (OH)3 }] ⋅ H2 O: A Layered Borate Built by Mixed Oxoboron Clusters with Nonlinear-Optical Property

A new acentric borate, K₂ Na₃ [{B₆ O₁₀ (OH)}-{B₃ O₄ (OH)₃ }] ⋅ H₂ O (1) has been made under solvothermal condition. 1 has layered structure made by B₆ O₁₃ (OH)-based chains and B₃ O₅ (OH)₃ -bridging clusters. Second-harmonic generation (SHG) measurements reveal that 1 is a phase-matchable nonlinear optical (NLO) material, showing the SHG signal intensity of 1.8 times that of KDP (KH₂ PO₄ ). Besides, UV-Vis diffuse reflectance spectrum shows that 1 has the short deep UV (DUV) absorption cutoff edge of 198 nm. Thermogravimetric analysis reveals it has good thermal stability. Also 1 represents firstly mixed oxoboron clusters-made 2D layered borate with NLO property.

LaTeBO5: a new borotellurite with a large birefringence activated by the highly distorted [Te(iv)O4] group

A new borotellurite, LaTeBO₅, containing the highly distorted [Te^(iv)O₄] group has been synthesized. Interestingly, it exhibits a wide ultraviolet transmittance range and large birefringence (0.080@1064 nm). The response electron distribution anisotropy approximation and dipole moment calculation demonstrate that the synergistic effect of the highly asymmetric [Te^(iv)O₄] and BO₃ groups is conducive to its large birefringence.

The First Mixed Calcium Zinc Borate with a Flexible [B8 O17 ] Fundamental Building Block and Short UV Cutoff Edge

The first mixed calcium zinc borate with a new fundamental building block (FBB) [B₈ O₁₇ ], Ca_1.13 Zn_0.87 B₈ O₁₄ has been successfully synthesized. It exhibits two independent interpenetrating three-dimensional B-O anion networks constructed by [B₈ O₁₇ ] groups, enriching the structural diversity of B-O configurations. In particular, the UV-Vis-NIR diffuse-reflectance spectrum shows that it has a short UV cutoff edge (<195 nm).

Cation Substitution of Hexagonal Triple Perovskites: A Case in Trimetallic Tellurates A2A'BTe2O9

Three new tellurates, namely, K₂BaPb_0.62Ba_0.38Te₂O₉ (1), Rb₂BaPb_0.7Ba_0.3Te₂O₉ (2), and Ba₂KLiTe₂O₉ (3), with hexagonal triple-perovskite structures have been designed via a cation substitution strategy. All three centrosymmetric compounds crystallize in the same hexagonal space group P6₃/mmc. In their structures, the [BTe₂O₉] (B = Pb/Ba for 1 and 2 and Li for 3) groups construct the final three-dimensional framework using face-sharing [Te₂O₉] dimmers and vertex-linked [BO₆] linkages. Meanwhile, the theoretical calculations demonstrate the numerical differences of their birefringence. Thermal stability analysis and differential scanning calorimetry were performed, and UV-vis-NIR diffuse reflectance spectra and infrared spectra of the three title compounds were also characterized and analyzed.

Bi2[B2(SeO3)6]: A Metal Boroselenite with a Unique Zero-Dimensional [B2(SeO3)6]6- Anionic Group and Large Birefringence

Explorations of new types of borates are important because of their promising application in diverse fields. A new bismuth-containing boroselenite, Bi₂[B₂(SeO₃)₆], has been obtained through high-temperature solid-state reaction in a closed system. Bi₂[B₂(SeO₃)₆] possesses a zero-dimensional [B₂(SeO₃)₆]^6- anionic group that does not belong to any types of reported boroselenites. Besides, Bi₂[B₂(SeO₃)₆] is the first boroselenite with lone-pair electrons containing a metal ion as the countercation. More interestingly, on the basis of the first-principles calculations, this compound displays a large birefringence (0.090) at 1064 nm.

In situ hydrothermal synthesis of polar second-order nonlinear optical selenate Na5(SeO4)(HSeO4)3(H2O)2

An alkali–metal selenate nonlinear optical (NLO) crystal, Na₅(SeO₄)(HSeO₄)₃(H₂O)₂, which possesses good second-order nonlinear optical properties, has been obtained by mild in situ hydrothermal synthesis.

KNa2ZrF7: A Mixed-Metal Fluoride Exhibits Phase-Matchable Second-Harmonic-Generation Effect and High Laser-Induced Damage Threshold

Halides are one type of important IR nonlinear-optical material candidate. Here, a mixed alkali metal and d⁰ transition-metal fluoride, namely, KNa₂ZrF₇, was obtained by a facile hydrothermal method. It crystallizes in an orthorhombic system with the polar space group Pmn2₁, and its pseudo-1D structure features isolated (ZrF₇)^3- moncocapped trigonal prisms, which are ionically linked together by countercations K⁺ and Na⁺, representing a new type of fluoride. The powder sample of KNa₂ZrF₇ exhibits a moderate second-harmonic-generation response and a high laser-induced damage threshold. Besides, it can realize phase matchability and possesses a wide-IR transparent window. Thermal stability analysis suggests that KNa₂ZrF₇ is a congruent compound. Structural comparisons with related fluorides and theoretical calculations are also presented in this work.

Borosulfates-Synthesis and Structural Chemistry of Silicate Analogue Compounds

Borosulfates are oxoanionic compounds consisting of condensed sulfur- and boron-centered tetrahedra. Hitherto, they were mostly achieved from solvothermal syntheses in SO3 -enriched sulfuric acid, or from reactions with the superacid H[B(HSO4 )4 ]. The crystal structures are very similar to those of the corresponding class of silicates and their substitution variants, especially regarding the typical structural motif of corner-sharing tetrahedra. However, the borosulfates are supposed to be even more versatile, because (BO3 ) units might also be part of the anionic network. The following article deals with detailed reports on the different synthesis strategies, the crystal chemistry of borosulfates in comparison to silicates, and their hitherto identified properties.

Sr5TeO2(BO3)4 and NaSr5(BO3)(SiO4)2: two inorganic metal borate derivatives with diverse zero dimensional anions

Two new inorganic metal borate derivatives, Sr₅TeO₂(BO₃)₄ and NaSr₅(BO₃)(SiO₄)₂, have been obtained through a high temperature solid reaction method. Sr₅TeO₂(BO₃)₄ crystallizes in a tetragonal space group of P4/mnc featuring a three-dimensional (3D) structure composed of a porous 3D strontium framework stabilized by the unique zero-dimensional (0D) [TeO₂(BO₃)₄]^10- anions. NaSr₅(BO₃)(SiO₄)₂ crystallizes in a monoclinic space group of P2₁/c with a 3D structure consisting of a splendid strontium 3D framework strengthened by isolated BO₃ and SiO₄ groups. The sodium cations located in the empty space of the structure. Thermal stability analyses, optical property measurements and theoretical studies of the compounds were performed. Refractive index calculations revealed that the birefringence of Sr₅TeO₂(BO₃)₄ and NaSr₅(BO₃)(SiO₄)₂ is 0.048 and 0.029, respectively, at 1064 nm.

Rb3BaTeB7O15: a novel [B7O16] fundamental building block in a new telluroborate with [TeO3] polyhedra

A new telluroborate Rb₃BaTeB₇O₁₅ with a new [B₇O₁₆] fundamental building block has been synthesized, and it is the first telluroborate that is constructed only by using [TeO₃] polyhedra.

Ba6BO3Cl9 and Pb6BO4Cl7: structural insights into ortho-borates with uncondensed BO4 tetrahedra

Two new halogen-rich ortho-borates, Ba₆BO₃Cl₉ and Pb₆BO₄Cl₇, were synthesized and characterized. Interestingly, Pb₆BO₄Cl₇ contains rare uncondensed BO₄ tetrahedra.

Ionothermal Synthesis of Metal Chalcogenides M2Ag3Sb3S7 (M = Rb, Cs) Displaying Nonlinear Optical Activity in the Infrared Region

Two interesting non-centrosymmetric metal chalcogenides, Rb₂Ag₃Sb₃S₇ and Cs₂Ag₃Sb₃S₇, were synthesized by an ionothermal approach. Crystals of compounds Rb₂Ag₃Sb₃S₇ and Cs₂Ag₃Sb₃S₇ possess isomorphic configuration, consisting of two-dimensional (2D) anionic networks _∞[Ag₃Sb₃S₇]^2-, which are split by alkali-metal M⁺ cations. The band gaps are 2.11 and 2.02 eV for Rb₂Ag₃Sb₃S₇ and Cs₂Ag₃Sb₃S₇, respectively. Second-harmonic generation (SHG) studies revealed that Rb₂Ag₃Sb₃S₇ affords a powder SHG performance of ∼0.5 × AgGaS₂ with type-I phase matching, while Cs₂Ag₃Sb₃S₇ shows a slightly stronger SHG performance of ∼0.6 × AgGaS₂ with type-I phase matching. Both compounds possess broad transparency ranges (∼0.6-20 μm), suggesting their potential as infrared (IR) nonlinear optical (NLO) materials. The laser damage thresholds (LDTs) of both Rb₂Ag₃Sb₃S₇ and Cs₂Ag₃Sb₃S₇ are about 2.3 × AgGaS₂. The calculated birefringence indexes Δn are 0.1885 and 0.1944 at 1.064 μm, respectively, which are sufficiently large enough to achieve phase matching. Theoretical studies using density functional theory have been implemented to further understand the relationship between their NLO properties and band structures.

Enhanced Persistence Properties through Modifying the Trap Depth and Density in Y3Al2Ga3O12:Ce3+,Yb3+ Phosphor by Co-doping B3

Long persistence phosphors with high emitting intensity are promising materials for safety signage and energy storage applications. Herein, an improved persistent luminescence of Y₃Al₂Ga₃O₁₂ phosphor by co-doping Ce³⁺, Yb³⁺, and B³⁺ is achieved using conventional solid-state reaction. On one hand, the incorporation of H₃BO₃ can improve the crystallinity; on the other hand, B³⁺ can replace Al³⁺/Ga³⁺ in tetrahedral sites in the host lattice, causing lattice contraction and modifying the trap depth and density. It is found that adding B³⁺ forms a much deeper trap with ∼1.10 eV depth. In addition, the density of the electron trap can also be dramatically increased compared to the sample without B³⁺. The charging process for persistent luminescence is demonstrated by comparing the photoluminescence excitation spectrum with the thermoluminescence excitation spectrum. The persistence luminescence mechanism is given by a visual energy level diagram on the basis of the vacuum referred binding energy scheme of Y₃Al₂Ga₃O₁₂.

Cs2CdV2O6Cl2 and Cs3CdV4O12Br: two new non-centrosymmetric oxyhalides containing d0 and d10 cations and exhibiting second harmonic generation activity

Two new non-centrosymmetric oxyhalides containing d⁰ and d¹⁰ cations and exhibiting strong second harmonic generation activity.