Crystalline Borate Research Articles

Structure and crystallizability of K2O-B2O3-SiO2 and K2O-B2O3-GeO2 glasses: Effect of composition and heat treatment mode

The stability and crystallizability of glasses K2O-B2O3-GeO2 and K2O-B2O3-SiO2 systems becomes an important consideration when selecting materials for optical purposes and the immobilization of radioactive wastes. To determine the crystallizability of boron-containing glasses, thermal treatments were carried out at 500 and 680 °C and the formed phases were identified. The structural features of the materials before and after treatment were studied by vibration spectroscopy. Glasses with B2O3/SiO2 = 2/5 and B2O3/GeO2 = 4/3 ratio proved to be the most resistant to heating. It was observed that the ratio of B/Si and B/Ge has a significant effect on crystallizability at any temperature. Heat treatment at 680 °C results in the formation of potassium borates, silicates, and borosilicates in the borosilicate system, while the crystallization of germanates and potassium borates is characteristic of the borogermanate system. Structural differences between the crystallization products of these two systems are shown to be due to the ability of germanium to form highly oriented structural units. With an increase in the B/Ge ratio, the crystallization of borogermanate glasses is shown to lead to a decrease in the proportion of crystalline borates. Conversely, during the crystallization of the borosilicate system, an increase in the B/Si ratio in the initial glass leads to an increase in their content.

Recent Progress in Crystalline Borates with Edge-Sharing BO4 Tetrahedra

Crystalline borates have received great attention due to their various structures and wide applications. For a long time, the corner-sharing B–O unit is considered a basic rule in borate structural chemistry. The Dy4B6O15 synthesized under high-pressure is the first oxoborate with edge-sharing [BO4] tetrahedra, while the KZnB3O6 is the first ambient pressure borate with the edge-sharing [BO4] tetrahedra. The edge-sharing connection modes greatly enrich the structural chemistry of borates and are expected to expand new applications in the future. In this review, we summarize the recent progress in crystalline borates with edge-sharing [BO4] tetrahedra. We discuss the synthesis, fundamental building blocks, structural features, and possible applications of these edge-sharing borates. Finally, we also discuss the future perspectives in this field.

Data Mining and Graph Network Deep Learning for Band Gap Prediction in Crystalline Borate Materials

Crystalline borates are an important class of functional materials with wide applications in photocatalysis and laser technologies. Obtaining their band gap values in a timely and precise manner is a great challenge in material design due to the issues of computational accuracy and cost of first-principles methods. Although machine learning (ML) techniques have shown great successes in predicting the versatile properties of materials, their practicality is often limited by the data set quality. Here, by using a combination of natural language processing searches and domain knowledge, we built an experimental database of inorganic borates, including their chemical compositions, band gaps, and crystal structures. We performed graph network deep learning to predict the band gaps of borates with accuracy, and the results agreed favorably with experimental measurements from the visible-light to the deep-ultraviolet (DUV) region. For a realistic screening problem, our ML model could correctly identify most of the investigated DUV borates. Furthermore, the extrapolative ability of the model was validated against our newly synthesized borate crystal Ag3B6O10NO3, supplemented by the discussion of an ML-based material design for structural analogues. The applications and interpretability of the ML model were also evaluated extensively. Finally, we implemented a web-based application, which could be utilized conveniently in material engineering for the desired band gap. The philosophy behind this study is to use cost-effective data mining techniques to build high-quality ML models, which can provide useful clues for further material design.

Role of alkali field strength on the speciation of Ni2+ in alkali borate glasses: comparison with crystalline Ni-borates

This work presents a comparative spectroscopic study of Ni speciation in binary alkali borate glasses, with up to 35 mol% alkali oxides, using optical absorption spectroscopy and Ni K-edge X-ray Absorption Near Edge Structure (XANES) and taking advantage of comparison with previous structural information obtained with Ni K-edge Extended X-ray Absorption Spectroscopy (EXAFS) on the same samples. Nickel-bearing K, Na or Li borate glasses exhibit an exceptional diversity of coloration (from green to yellow, brown, and purple). This is due to a progressive coordination change of Ni2+ with increasing alkali content, from 6-, to 5- and 4-Ni coordination, each coordination state having a peculiar structural significance. [6]Ni2+ is predominant in low alkali borate glasses, where Ni octahedra cluster in ordered Ni-rich domains. [4]Ni2+ is formed at low alkali cation field strength: it predominates in high potassic glasses but it is only a minor coordination state in Na-borate glasses and it is absent in Li-borate glasses, in which, by contrast, [5]Ni2+ prevails. For these three coordination states, the comparison with the structure of crystalline borates suggests a diversity of linkages between Ni2+ and the borate polymeric network. Among the alkali borate glasses investigated, each Ni-coordination state shows similar spectroscopic properties. This implies that the modification of Ni speciation with glass composition arises only from a variation of the relative contribution of 6-, 5- and 4-coordinated Ni2+ without significant modification of the spectroscopic parameters characteristic of each site. The coordination number of Ni2+ is correlated with the field strength of the modifier cations present in the glass: higher the field strength of the modifier cations, higher the nickel coordination number. High-K borate glasses favor the formation of [4]Ni2+, as this coordination state is not observed in Li- and is only minority in Na borate glasses, because of Li and Na preference for charge compensating [4]B instead of [4]Ni2+. Due to the similarities between Ni2+ and Mg2+, the diversity of the structural scenarios around Ni2+ in alkali borate glasses may shed light on the structural behavior of Mg in the same glasses, providing additional evidence of the control of Mg coordination by the field strength of the alkalis.

Expanding the chemistry of borates with functional [BO2]\u2212 anions

More than 3900 crystalline borates, including borate minerals and synthetic inorganic borates, in addition to a wealth of industrially-important boron-containing glasses, have been discovered and characterized. Of these compounds, 99.9 % contain only the traditional triangular BO3 and tetrahedral BO4 units, which polymerize into superstructural motifs. Herein, a mixed metal K5Ba2(B10O17)2(BO2) with linear BO2 structural units was obtained, pushing the boundaries of structural diversity and providing a direct strategy toward the maximum thresholds of birefringence for optical materials design. 11B solid-state nuclear magnetic resonance (NMR) is a ubiquitous tool in the study of glasses and optical materials; here, density functional theory-based NMR crystallography guided the direct characterization of BO2 structural units. The full anisotropic shift and quadrupolar tensors of linear BO2 were extracted from K5Ba2(B10O17)2(BO2) containing BO2, BO3, and BO4 and serve as guides to the identification of this powerful moiety in future and, potentially, previously-characterized borate minerals, ceramics, and glasses.

Thermoluminescence and photoluminescence of magnesium-doped lithium tetraborate nanoparticles

Mg-doped Li2B4O7 nanophosphor was synthesized for the first time by using solid-state method, and the influence of magnesium dopant on the thermoluminescence dosimetry features was investigated. X-ray powder diffraction, scanning electron microscopy (SEM), photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy analyses were utilized for identifying crystalline structure, morphology, particle size, borate groups and optical properties of the synthesized nanophosphor. Thermoluminescence sensitivity was enhanced by introducing magnesium dopant in LTB and reached a maximum at 0.5 mol% of impurity. The optimum pre-irradiation annealing regime was found at 400 °C for 15 min. Kinetic parameters and dosimetry characteristics, such as fading, dose response and reusability, are also presented and discussed.

Crystal Chemistry of High-Temperature Borates.

In recent years borate-based crystals has attracted substantial interest among the research community. The overall importance of this family of materials is reflected in miscellaneous articles and several reviews that have been published over the years. Crystalline borate materials exhibit numerous interesting physical properties, which make them promising for further practical applications. Diversity of functional characteristics results from their high structural flexibility caused in the linkage of planar/non–planar BO3 groups and BO4 tetrahedra, which can occur as isolated or condensed structural units. This report is a brief review on crystal chemistry and structure features of anhydrous/high-temperature borates. Polymorphism of boron-oxygen radicals has been considered basing on cations’ nature and synthesis conditions. Analysis of the laws governing borates structures and general principles of their systematics was discussed. As a result, an alternative classification of anhydrous compounds has been considered. It is based on four orders of their subdivision: (1) by the variety of anion formers, (2) by the cation charge, (3) by the N = NM:NB, i.e., ratio of metal atoms number to the ratio of boron atoms number (N-factor) value indicating the borate structural type (if it is known), (4) by the cation type and size.

Characterization of crystalline borates prepared from solution and derived glasses

An aqueous solution route has been developed to prepare calcium sodium borate compositions of the formula xB2O3·(100–x)(0.5CaO·0.45Na2O·0.05P2O5) (36.2 ≤ x ≤ 61.3 mol%). The effect of heat-treatment and melt-quenching on the structure and physical properties was investigated using differential thermal analysis, X-ray diffraction, FTIR spectroscopy, 11B MAS NMR and density. Dried powders were heat treated at temperatures 400–800 °C for 3h. XRD revealed formation of crystalline Na2B4O7·5H2O, Ca5(PO4)3OH, Na3B5O9H2O and CaB3O5(OH) in the samples treated up to 500 °C. Samples treated at higher temperature show the presence of CaNaB5O9, CaNa3B5O10 and CaNaPO4. Quenched solids obtained by melting powders are amorphous. It is deduced from FTIR spectra that CaO and Na2O modify the borate network forming BO4 and BO3 with non-bridging units, which depend on the molar ratio R =(Na2O+CaO)/B2O3 and temperature. The fraction N4 of four coordinated boron atoms changes with R and can be predicted by treating the compositions as if they are mixtures of Na2O–B2O3 and CaO–B2O3 matrices. N4 values have been used to calculate the fraction of all units in the glass structure. The results are confirmed by 11B MAS NMR spectra that show the presence of symmetric and asymmetric trigonal BO3 groups and splitting line shape of [4]B. The latter is assumed being related to different four-coordinated boron environments. Density and molar volume obtained by using mixed matrices concept agree well with the experimental data.

Engineering Materials for Progressive All-Solid-State Na Batteries

Following the prevalence of the Li-ion battery for electrical energy storage systems (EESs), the world is looking toward alternative, cost-effective, electrical EESs for portable electronics, electric vehicles, and grid storage from renewable sources. Na-based batteries are the most promising candidates and show similar chemistry as Li-based batteries. All-solid-state sodium batteries (AS3Bs) have attracted great attention due to safe operation, high energy density, and wide operational temperature. Herein, current development of solid-state crystalline borate- and chalcogenide-based Na-ion conductors is discussed together with historically important Na-β-alumina and Na superionic conductors (NASICONs). Furthermore, we report on engineering a ceramic Na-ion electrolyte and electrode interface, which is considered a bottleneck for practical applications of solid-state electrolytes in AS3Bs. A soft Na-ion conducting interlayer is critical to suppress the interfacial Na-ion charge transfer resistance between...

11B and 7Li MAS NMR of glassy and crystalline borate compounds

11B and 7Li MAS NMR of glassy and crystalline borate compounds

English

English

Vibrational spectra and factor group analysis of rare-earth chromium borates, RCr3(BO3)4, with R = La–Ho

Anhydrous orthoborates RM3(BO3)4, where R=Y, La–Lu, M=Al, Ga, Cr, Fe, with huntite structure type are considered as multifunctional laser materials. The crystal structure of these borates is either rhombohedral with space group R32 (D37) (Z=3) or monoclinic with space group C2/c (C2h6) (Z=4) depending on the growth conditions. Both modifications have very close polytypic structures, and it is difficult to identify them by powder diffraction data. In this context, double borates of rare-earth cations and Cr3+ have been grown from high-temperature solutions and are characterized by Raman and infrared spectroscopy in a crystalline state in combination with factor group analysis of vibrational modes. The assignment for the stretching and bending vibrations of BO33− groups and external modes has been made. Some external modes have been identified by study of mass effect (Al–Cr, La–Ho). Comparison of the Raman spectra of these borates shows redistribution of band intensities of two spectral modifications, related to different symmetry groups. As predicted by factor group analysis, the number of IR-active vibrational modes of stretching and bending vibrations of BO33− units significantly increases in infrared spectra of monoclinic borates in comparison with rhombohedral ones. The dependence of the realized borate space group on the crystal growth conditions and the sort of rare-earth atom was revealed. Both GdCr3(BO3)4 and EuCr3(BO3)4 borates crystallize in space group R32 irrespective of growth conditions. The borates with the large rare-earth elements La–Nd always form the monoclinic structures, irrespective of crystallization temperature. The borates SmCr3(BO3)4, TbCr3(BO3)4 and DyCr3(BO3)4 have been obtained in two modifications in dependence of crystalline borate substance/solvent ratio and related temperature of crystallization.

Influence of corrosion processes on the head loss across ECCS sump strainers

Abstract Corrosion investigations were carried out using hot-dip galvanized steel samples in order to identify the corrosion mechanisms as well as the nature of corrosion products formed. Corrosion of grating treads may exacerbate ECCS strainer clogging problems during LOCA events in LWR. For the related experiments, tailored bench-scale facilities have been constructed. The results of batch experiments as well as of long-time corrosion investigations in the Korr VA test facility suggest that there is a multi-stage corrosion process. The first stage comprises the dissolution of the Zn layer in the coolant forming Zn2+ ions, which can generate crystalline zinc borate in boric acid solutions, if the ion concentration exceeds the saturation concentration. The base material (steel) is cathodically protected as long as the zinc layer is present. During the second stage, the base material dissolves forming insoluble corrosion particles, which can subsequently lead to acceleration of the strainer clogging. The main influences on corrosion were identified as impact of the water onto the corroding surface, water chemistry and Zn surface/coolant volume ratio.

ChemInform Abstract: Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

Anders als die anderen: Neptuniumborate unterscheiden sich von Uran- und Plutoniumboraten: Sie liegen als gemischtvalente Verbindungen mit jeweils dreierlei Koordinationsumgebungen und Oxidationstufen vor (siehe Bild; Polyeder: NpIV hellblau, NpV dunkelblau, NpVI grün, B gelb; Kugeln: O rot, K oder Ba blau).

Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage

In contrast to uranium and plutonium borates, neptunium borates are mixed-valent and simultaneously display three coordination environments and three oxidation states.

Chemoselective Boron–Carbon Bond Cleavage by Hydroboration of Borirenes

We report on the hydroboration of 1-[bis(trimethylsilyl)amino]-2,3-diethylborirene (3) with 9-borabicyclo[3.3.1]nonane (9-BBN), which led through ring-opening to an amino(vinyl)borane. The viscous borane was subsequently converted into a crystalline borate on treatment with MeLi. Both compounds were fully characterized by multinuclear NMR spectroscopy and in case of the latter by single-crystal X-ray diffraction analysis. To elucidate the reaction mechanism of the unexpected boron-carbon bond cleavage, DFT calculations of energy minima and transition states for the hydroboration were carried out.

Chemical-bond analysis of the nonlinear optical properties of the borate crystals LiB 3 O 5 , CsLiB 6 O 10 , and CsB 3 O 5

The second-order nonlinear optical properties of practical borate crystals, LiB3O5, CsLiB6O10, and CsB3O5, which all contain the identical basic structural unit [the (B3O7)5- group], have been quantitatively studied from the chemical-bond viewpoint. Differences in the nonlinear optical properties among these three borate crystals arise from the contributions of the different cations, i.e., the different interaction between the cation and the (B3O7)5- anionic group. The chemical-bond method quantitatively expresses this important difference. At the same time, the current calculation also shows that the B3O7 group is a very important crystallographic frame in the crystalline borate solids; it offers different cations an excellent coordination environment.

A comparison of crystalline and vitreous lead borates using laser photoionization mass spectroscopy

A high resolution, laser desorption time of flight mass spectrometer (LITOF-MS) was used to study lead borate glasses and crystals. This technique provides valuable information about glass structure, including the superstructural network units. Several structural units were identified and we found evidence of a lead substructure beginning to form in the glass with increased lead content.

EPR STUDY OF Fe3+ AND Mn2+ DOPED AMORPHOUS AND CRYSTALLINE ALUMINUM BORATES

Amorphous and crystalline aluminum borates prepared by sol–gel method doped with iron and manganese were studied by electron paramagnetic resonance in order to determine the matrix effects on Fe3+ and Mn2+ environments during their consolidation by heat treatment up to 860°C. In amorphous matrices, after heat treatments up to 600°C, the Fe3+ environment is almost unaffected but the vicinity of Mn2+ ions is relatively strongly disordered. In partial crystalline alumina and aluminum borate samples, obtained after heat treatments applied at 860°C, the Fe3+ sites are subjected to completely different crystalline fields, as regards intensity and symmetry. If in crystalline alumina we have both sites typical for α and γ phases in crystalline aluminum borate, the well-known spectrum of Fe3+ in disordered systems seems to be solved, suggesting more than one well-defined site. In the case of manganese-doped samples, only a diminishing of hyperfine resolution with increasing heat treatment temperature is observed as a result of environment distortion by improvement of alumina borate sample crystallinity.