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Results for “crystallization”

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DOE OSTI2016

Single crystal structure and SHG of defect pyrochlores CsB{sup V}MoO{sub 6} (B{sup V}=Nb,Ta)

The crystal structure and non-linear optical properties of CsNbMoO{sub 6} and CsTaMoO{sub 6} defect pyrochlores have been studied. The single crystals of these compounds grown by the flux method possess an octahedral faceting and reach up to 50 µm in size. The crystal structures of CsB{sup V}MoO{sub 6} (B{sup V}=Nb, Ta) were investigated by X-ray diffraction method. Both compounds crystallize in the cubic symmetry with noncentrosymmetric space group F-43m. The second harmonic generation of CsNbMoO{sub 6} and CsTaMoO{sub 6}was found to be 1.6×10{sup −2} and 8.5×10{sup −4} of lithium niobate, correspondingly. It has been determined that distortions of [MO{sub 6}] polyhedra (M=Nb, Ta, Mo) as well as polarizability and covalency of Nb–O and Ta–O bonds have a great effect on the second harmonic generation. - Highlights: • CsNbMoO{sub 6} and CsTaMoO{sub 6} homogeneous single crystals have been grown. • The crystal structure of CsTaMoO{sub 6} has been studied. • Nonlinear optical properties of CsNbMoO{sub 6} and CsTaMoO{sub 6} have been found. • The microscopic origin of the second harmonic generation (SHG) response have been identified.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Crystallization study of amorphous sputtered NiTi bi-layer thin film

The crystallization of Ni-rich/NiTiCu bi-layer thin film deposited by magnetron sputtering from two separate alloy targets was investigated. To achieve the shape memory effect, the NiTi thin films deposited at room temperature with amorphous structure were annealed at 773 K for 15, 30, and 60 min for crystallization. Characterization of the films was carried out by differential scanning calorimetry to indicate the crystallization temperature, grazing incidence X-ray diffraction to identify the phase structures, atomic force microscopy to evaluate surface morphology, scanning transmission electron microscopy to study the cross section of the thin films. The results show that the structure of the annealed thin films strongly depends on the temperature and time of the annealing. Crystalline grains nucleated first at the surface and then grew inward to form columnar grains. Furthermore, the crystallization behavior was markedly affected by composition variations. - Highlights: • A developed bi-layer Ni45TiCu5/Ni50.8Ti was deposited on Si substrate and crystallized. • During crystallization, The Ni{sub 45}TiCu{sub 5} layer is thermally less stable than the Ni-rich layer. • The activation energy is 302 and 464 kJ/mol for Cu-rich and Ni-rich layer in bi-layer, respectively.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Crystallization kinetics of Mg–Cu–Yb–Ca–Ag metallic glasses

The paper presents research into a Mg–Cu–Yb system based metallic glassy alloys. Metallic glasses were prepared using induction melting and further injection on a spinning copper wheel. The effect of alloying by Ag and Ca on the glass forming ability and the kinetics of crystallization of Mg–Cu–Yb system based alloys were studied. The differential scanning calorimeter and X-ray diffractometer were used to investigate the kinetics of crystallization and the phase composition of the samples. An indicator of glass forming ability, effective activation energy of crystallization, and enthalpy of mixing were calculated. An increase of the Ca and Ag content has a positive effect on the glass forming ability, the effective activation energy of crystallization, and the enthalpy of mixing. The highest indicators of the glass forming ability and the thermal stability were found for alloys that contain both alloying elements. The Ag addition suppresses precipitation of the Mg{sub 2}Cu phase during crystallization. A dual-phase glassy-nanocrystalline Mg structure was obtained in Mg{sub 65}Cu{sub 25}Yb{sub 10} and Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} alloys after annealing. Bulk samples with a composite glassy-crystalline structure were obtained in Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} and Mg{sub 64}Cu{sub 21}Yb{sub 9.5}Ag{sub 5.5} alloys. A thermodynamic database for the Mg–Cu–Yb–Ca–Ag system was created to compare the process of crystallization of alloys with polythermal sections of the Mg–Cu–Yb–Ca–Ag phase diagram. - Highlights: • New alloy compositions based on Mg–Cu–Yb system were developed and investigated. • Increasing content of Ag and Ca leads to improving GFA. • Bulk samples with a composite glassy-crystalline structure were obtained. • Thermodynamic database for Mg–Cu–Yb–Ca–Ag system was created.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Semiorganic nonlinear optical material: Crystal growth, structure and optical properties of NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2}

Graphical abstract: - Highlights: • Semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3}. • It crystallizes in the noncentrosymmetric Monoclinic space group P2. • Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280. • NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has an absorption edge about 220 nm in the UV region. • It exhibits a NLO efficiency of about two times that of KDP (KH{sub 2}PO{sub 4}) standard. - Abstract: Single crystal of the semiorganic NLO material NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} has been grown with sizes up to 8 × 5 × 2 mm{sup 3} by the slow evaporation method. The crystal structure of this compound was determined by single crystal X-ray diffraction. It crystallizes in the Monoclinic space group P2 with lattice parameters a = 5.4045(11) Å, b = 11.692(2) Å, c = 9.4773(19) Å and Z = 2. Thermal analysis demonstrated NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} are thermally stable up to 280 °C. NaB(L-C{sub 4}H{sub 4}O{sub 5}){sub 2} exhibits an absorption edge about 220 nm in the UV region. The powder second-harmonic generation (SHG) measurement performed on the ground crystal indicates that it has a NLO efficiency of about 2 times that of KDP (KH{sub 2}PO{sub 4}) standard. In addition, the origin of stronger SHG effect was discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Synthesis and in situ high pressure Raman spectroscopy study of AlN dendritic crystal

Graphical abstract: - Highlights: • The sample is the typical dendritic crystal structure. • The phase transition of AlN dendritic crystal is researched. • The Raman signal of rock salt AlN is observed under high pressure. • Grüneisen parameters and phase transition criterion are discussed. - Abstract: AlN dendritic crystal was synthesized by the direct current arc discharge apparatus. X-ray diffraction (XRD) patterns indicated that the sample is hexagonal AlN and preferentially grown along the a-axis direction. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) images reveal that the product mainly consists of micron AlN dendritic crystal. In situ high pressure Raman spectra of AlN dendritic crystal has been measured in the pressure ranged from ambient pressure to 32.97 GPa at room temperature by using diamond anvil cell. According to the Raman scattering results, the phase transition from the wurtzite to rock salt was found at about 20.73 GPa by the appearance of a new Raman signal. Above 20.73 GPa, a new Raman signal due to disorder-activated Raman scattering in the rock salt phase was observed. In addition, the pressure coefficients, phase transition criterion, and mode Grüneisen parameters of AlN dendritic crystal, which could be different from that of other AlN, are carefully discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Luminescence and radiation resistance of undoped NaI crystals

Highlights: • The performance of NaI scintillators depends on luminescence properties. • A criterion of crystals’ purity level is radiation colorability at room temperature. • The traces of the most dangerous impurities were detected. • Crucial role in efficiency of pure NaI scintillator play the crystal perfection. - Abstract: Undoped NaI single crystal is an excellent scintillator at low temperature. However, scintillation parameters of different quality crystals vary in a wide range, significantly exceeding measurement error. Experimental data demonstrate the features of luminescence, radiation induced coloration, and afterglow dependence on the quality of nominally pure crystals. It is found that defects level that allows to elucidate artefacts introduced by traces of harmful impurities corresponds to 3 × 10{sup 15} cm{sup −3} that significantly overhead accuracy of chemical and absorption analysis. It is shown that special raw material treatment before and during the single crystal growth allows to reach NaI purity level that avoids impurities influence to the basic luminescence data.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Effect of the purity of starting materials on the growth and properties of potassium dihydrogen phosphate single crystals – A comparative study

Highlights: • Bulk size KDP crystal has been grown with higher growth rate. • Systematic study on the effect of starting materials has been done. • Crystalline perfection is maintained in the entire crystal. - Abstract: A systematic study on the effect of purity of starting materials on the growth and properties of potassium dihydrogen phosphate single crystals is crucial for the future study of the material for nonlinear optical applications. Potassium dihydrogen phosphate crystals were grown using high pure (99.999%) and ordinary (99.9%) starting raw materials using slow cooling method in identical conditions. Their optical transparency and crystalline perfection are studied by UV and high resolution X-ray diffraction analyses respectively. The results are checked with the help of etching analyses. The full width at half maximum is 8″ which is close to that expected from the plane wave theory of dynamical X-ray diffraction for an ideally perfect crystal. Results of those studies are correlated with each other. The quantitative results show that the raw material plays an important role in the growth of good quality crystals.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Preparation of Gd(OH){sub 3} large single crystals by solid KOH assisted hydrothermal method and their luminescent and magnetic properties

Highlights: • Gd(OH){sub 3} large single crystals were prepared by solid KOH assisted hydrothermal method. • The possible growth mechanism of Gd(OH){sub 3} large single crystals was proposed. • The Gd(OH){sub 3} samples emitted a strong narrow-band ultraviolet B (NB-UVB) light. • The Gd(OH){sub 3} samples showed good paramagnetic properties. - Abstract: Large single crystals of gadolinium hydroxide [Gd(OH){sub 3}] in the length of several millimeters were successfully prepared by using solid KOH assisted hydrothermal method. Gd(OH){sub 3} samples were characterized by X-ray diffraction (XRD), 4-circle single-crystal diffraction, Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). FESEM image shows hexagonal prism morphology for the Gd(OH){sub 3} large crystals. The possible growth mechanism of Gd(OH){sub 3} large single crystals was proposed. The photoluminescence and magnetic properties of Gd(OH){sub 3} species were investigated.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Synthesis, growth, structure, mechanical and optical properties of a new semi-organic 2-methyl imidazolium dihydrogen phosphate single crystal

Highlights: • 2MIDP crystals were grown by slow evaporation solution growth technique. • Single crystal XRD revealed self-assembled supramolecular framework. • Z scan technique is employed for third order nonlinear optical susceptibility. • Structure-property correlation is established. - Abstract: A new semi-organic compound, 2-methyl imidazolium dihydrogen phosphate (2MIDP), was prepared and good quality single crystals of 2MIDP were grown by slow evaporation solution growth technique. Crystal structure elucidated using Single crystal XRD showed that 2MIDP crystallizes in monoclinic system with P2{sub 1}/c space group. FT-IR, UV-Vis-NIR, Fluorescence and FT-NMR spectra confirm the molecular structure of 2MIDP. The UV-Vis-NIR spectra established the suitability of the compound for NLO applications. TG-DSC showed that 2MIDP is thermally stable up to 200 °C. Mechanical characteristics like hardness number (H{sub v}), stiffness constant (C{sub 11}), yield strength (σ{sub v}), fracture toughness (K{sub c}) and brittleness index (B{sub i}) were assessed using Vicker’s microhardness tester. Third order nonlinear optical properties determined from Z-scan measurement using femto and picosecond lasers showed two photon reverse saturable absorption. The enhancement of nonlinear optical properties in femto second laser, revealed the suitability of 2MIDP for optical limiting applications.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Single crystal growth and variation of thermodynamic and magnetic properties of Pr1−xLaxAlO3 (x = 0, 0.8)

Highlights: • The perovskite Pr{sub (1-x)}La{sub (x)}AlO{sub 3} was grown by two different protocols to control the P{sup 4+} concentration. • Low temperature magnetic properties in bulk single crystals are sensitive to annealing protocols. • Post growth annealing in a reducing atmosphere leads to closest Pr{sub 0.2}La{sub 0.8}AlO{sub 3} stoichiometry. • A possible new magnetic transition for single crystal PrAlO{sub 3} is observed at 6 K. - Abstract: Two approaches to using optical floating zone (OFZ) technique for single crystal growth of the perovskite Pr{sub 1−x}La{sub x}AlO{sub 3} are discussed, along with the influence on the physical properties of the resulting single crystals due to oxidizing and reducing post anneals. In method one (M1) we used pre-reduced Pr{sub 2}O{sub 3} powder starting material, while in the other method, M2, we employed an argon 5% hydrogen reducing environment during the floating zone single crystal growth. Magnetic susceptibility of the low temperature monoclinic phase of Pr{sub 0.2}La{sub 0.8}AlO{sub 3} is shown to be sensitive to the precise annealing protocol followed. For the post-growth reduced single crystal the magnetic susceptibility is flat across the R-3c to C2/m structural transition, whereas the oxidized and as-grown samples display a sharp upturn and downturn, respectively. We attribute the low temperature susceptibility differences to relative proportions of Pr{sup 3+} and Pr{sup 4+}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Optimization of crystal growth and properties of γ-CuI ultrafast scintillator by the addition of LiI

Highlights: • Large and transparent γ-CuI single crystal with the size over 20 mm was successfully obtained for the first time. • The intensities of near-band-edge emissions of γ-CuI single crystal are greatly enhanced by Li and I dopants. • The 430 nm emission decay time is less than 450 ps under pulsed X-ray irradiation. - Abstract: Large-sized γ-CuI single crystals with ultrafast scintillation property were grown in LiI acetonitrile solvent through evaporation technique. The LiI exhibits unique properties to γ-CuI single crystal preparation. One is that it increases the solubility of CuI in the solvent, which gives rise to a largest-sized (23 × 14 × 2 mm{sup 3}) single crystal with the high optical transmission (over 60%) in the wavelength region of 435–800 nm. The other feature is that it acts as an effective isoelectronic dopant and improves the molar ratio of copper to iodine, which greatly enhances the near-band-edge emissions (411 and 432 nm) and suppresses the broadband emission (680 nm). The decay time of the fast emission under pulsed X-ray excitation is shorter than 450 ps. The results will give a guidance for optimizing the properties of γ-CuI single crystal as an ultrafast scintillator.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Flux growth and optical properties of K7CaY2(B5O10)3 nonlinear crystal

Highlights: • K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} crystals were grown from new flux. • SHG efficiency for K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} crystals is comparable to that of KDP. • K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} crystals have UV cut off edge at 190 nm. - Abstract: Non-centrosymmetric borates K{sub 7}CaY{sub 2}(B{sub 5}O{sub 10}){sub 3} have been synthesized by solid state reaction and the crystals were successfully grown by the top seeded solution growth method using K{sub 2}O-B{sub 2}O{sub 3}-CaF{sub 2} flux. According to the single X-ray diffraction, the structure belongs to the R32 space group with lattice parameters a = 13.2516(2) Å and c = 14.9679(3) Å. IR, Raman, absorption spectra as well as data on melting temperature were obtained for the crystal. The short edge of UV absorption and SHG intensity comparable with KH{sub 2}PO{sub 4} (KDP) suggests that this crystal is a promising nonlinear-optical material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2014

Towards increased waste loading in high level waste glasses: Developing a better understanding of crystallization behavior

A number of waste components in US defense high level radioactive wastes (HLW) have proven challenging for current Joule heated ceramic melter (JCHM) operations and have limited the ability to increase waste loadings beyond already realized levels. Many of these ''troublesome'' waste species cause crystallization in the glass melt that can negatively impact product quality or have a deleterious effect on melter processing. Thus, recent efforts at US Department of Energy laboratories have focused on understanding crystallization behavior within HLW glass melts and investigating approaches to mitigate the impacts of crystallization so that increases in waste loading can be realized. Advanced glass formulations have been developed to highlight the unique benefits of next-generation melter technologies such as the Cold Crucible Induction Melter (CCIM). Crystal-tolerant HLW glasses have been investigated to allow sparingly soluble components such as chromium to crystallize in the melter but pass out of the melter before accumulating. The Hanford site AZ-101 tank waste composition represents a waste group that is waste loading limited primarily due to high concentrations of Fe 2 O 3 (with higher Al 2 O 3 ). Systematic glass formulation development utilizing slightly higher process temperatures and higher tolerance to spinel crystals demonstrated that an increase in waste loading of more than 20% could be achieved for this waste composition, and by extension higher loadings for wastes in the same group.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2021

A universal etching method for synthesizing high-performance single crystal cathode materials

LiNi x MnyCo 1-x-y O 2 (NMC) is considered the most appealing cathode material due to its high energy density and low cost. However, the stability and safety concerns, caused by the degradation of polycrystalline cathode materials during cycling, have restricted their practical applications. To overcome this shortcoming, converting polycrystalline cathode to high-performance single-crystal cathode materials becomes an appealing solution. In this work, a universal etching approach is firstly developed to synthesize single-crystal cathode materials. The rate performance of the obtained single-crystal NMC111 is 10–15% more than that of polycrystalline NMC111 whereas the capacity retention of single-crystal NMC111 is enhanced by ~12% after 300 cycles at 0.5C. The obtained single-crystal NMC622 exhibits a pronounced improvement in rate performance, especially at high rates (~28.6% better at 5C and ~129% better at 10C) and has a comparable cycle performance compared to polycrystalline NMC622. Altogether, the findings propose an alternative approach to generate single-crystal particles with high energy density and cycle stability for the next generation lithium-ion batteries.

25 ENERGY STORAGE↗

DOE OSTI2022

Molecular dynamics simulation of seeded crystal growth in glass

The mechanism of non-congruent growth of a crystal from glass has been sought using molecular dynamics simulations. Specifically, as a model of this process, the growth of a lithium niobate (LiNbO 3 ) crystal seed sandwiched between two lithium niobosilicate (LNS) glass slabs has been simulated as a function of time and temperature. The growth of pre-existing crystal is strongly affected by the orientation of crystal seed, temperature, and the SiO 2 concentration in the surrounding LNS glass matrix. The orientation of LiNbO 3 seed surface that has inherently larger interplanar distance results in a relatively slower crystal growth. The addition of SiO 2 to LNS system significantly decreases the crystal growth, which primarily occurs in the region devoid of Si. The suppressive effect of SiO 2 on growth rate can be traced to the existence of defect complex comprising of Si substituted at the Nb site and a nearby Nb vacancy.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Exploring competitive metal binding and crystallization of UO 2 2+ and Cu 2+ tetrahydrofuran-2,3,4,5-tetracarboxylic acid complexes

Solvent extractions are used to separate actinide elements from fission products in nuclear waste streams and the successful isolation of specific species utilize subtle differences in metal ligand binding. Metal ligand binding is also important in crystallization of metal organic materials and herein we explore the importance of competitive binding in the tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THFTCA) system. This ligand has been previously evaluated for the selective extraction of uranium from other lanthanides and actinides and in the current research, we evaluate the crystallization of uranyl-THFTCA complexes in the presence of Cu 2+ , Sr 2+ , Th 4+ , and Ce 3+ . Three major phases were formed in the crystallization experiments and characterized with single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, and Raman spectroscopy. Two of the resulting phases were novel (UTHF1 ((C 4 H 10 N 2 )[UO 2 (C 8 H 8 O 9 ) 2 ]∙2H 2 O) and UTHF2 (Na[(UO 2 )(C 8 H 5 O 9 )(H 2 O)]∙ 3.5 H 2 O)), whereas the third (CuTHF1) was previously reported in the literature. Raman spectroscopy was utilized to evaluate spectral changes in the mother liquor of UTHF1, UTHF2, and CuTHF1 over time to assess the crystallization process. Further, isothermal titration calorimetry was used to determine the binding constants for UO 2 2+ and Cu 2+ to the THFTCA ligand in solution and evaluate the role of competitive metal binding in this system. The thermodynamic parameters and the crystallographic data were used to justify the formation of a weaker UO 2 2+ -THFTCA complex. Formation of a weaker UO 2 2+ -THFTCA complex supports our findings that UTHF1 only forms in homomeric systems, but suggests that the crystallization of UTHF2 and CuTHF1 is reliant on the presence of additional counter ions and ligands to change the amount of available THFTCA ligand.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Direct Air Capture of CO 2 via Reactive Crystallization

Atmospheric CO 2 removal using engineered chemical processes, aka direct air capture (DAC), has become an essential component of our available portfolio for mitigating climate change. Here we describe a promising approach to DAC based on reactive crystallization of atmospheric CO 2 (RC-DAC) with aqueous guanidine and amino acid. Compared to the previously studied phase-changing DAC processes involving initial CO 2 absorption by an aqueous alkaline solvent followed by carbonate crystallization in a second step, RC-DAC combines the CO 2 absorption and carbonate crystallization into a single step. Thus, as the insoluble carbonate salts are removed from solution by crystallization, more CO 2 is pulled from the air into solution, further driving the DAC process. The RC-DAC was performed in a household humidifier as the air–liquid contactor, which can handle solid–liquid slurries effectively. The crystallization was monitored in situ by pH measurements, real-time imaging with a microscope probe, and by Raman spectroscopy, and ex situ by NMR spectroscopy, powder X-ray diffraction, and total inorganic carbonate analysis. Further, the investigation provided a detailed mechanistic picture of the RC-DAC process, involving formation of carbamate and carbonate anions in solution, followed by sequential crystallization of different guanidinium carbonate phases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Rapid Crystallization of Zeolites with Controllable Defects: Disentangling Fluoride Concentration and pH Using NH 4 F

Zeolite synthesis is typically conducted either under basic conditions or in neutral fluoride media using hydrofluoric acid (HF). While basic (OH − ) conditions generally result in faster zeolite crystallization, they can also increase the likelihood of framework defects and crystal intergrowths. In contrast, synthesis in neutral fluoride media tends to produce fewer defects because fluoride balances positive charges from structure-directing agents. However, this method often requires significantly longer crystallization times and involves the handling of dangerous HF. In the present study, we pursue the best of both synthesis conditions, rapid syntheses with controllable defect concentrations, by disentangling of mineralizing agent and chargebalancing agent using ammonium fluoride (NH 4 F) as an alternative to HF. We have investigated the use of NH 4 F in the syntheses of siliceous and aluminum-containing zeolite A (LTA, small pore), ZSM-5 (MFI, medium pore), and siliceous Beta(*BEA, large pore). The crystallization times of all four zeolites decreased substantially with an increasing NH 4 F concentration. Crystallization times were reduced from 24 to 4 h (Si-LTA), 96 to 36 h (Al-LTA), 240 to 6 h (ZSM-5), and 24 to 3 h (Si-*BEA). Additionally, increasing the NH 4 F concentration in the synthesis mixtures decreases the defect densities of siliceous zeolites. Raman spectroscopy, along with 29 Si MAS NMR, 19 F MAS NMR, 13 C MAS NMR, and fluorine elemental analysis of Si-LTA samples confirms that the reduction in charged defects (Si−O − ) is due to the higher incorporation of F − within the double four-membered ring (D4R) present in the LTA samples. We show that the accelerated crystallization is due to the role of F − in enhancing the silica mineralization rate (formation of silicon hexafluoride species) and stabilizing D4Rs under basic conditions. As a result, combining basic and fluoride-mediated synthesis could therefore be advantageous for faster zeolite production and improved control over structural properties for a wide variety of zeolite structures.

Anions↗