Controlled Crystallization Method Research Articles

Citric acid-assisted synthesis of FeFe(CN)6 with reduced defects and high specific surface area for aqueous zinc–sodium hybrid batteries

With citric acid as an additive, low-defect C-FeFe(CN)6 with small grain size and high specific surface area was successfully prepared using a controlled crystallization method.

Luminescence, optical and temperature sensitive characteristics of Tm3+ /Yb3+ doped fluoride phosphosilicate glass ceramics

Yb3+/Tm3+ doped fluoride phosphosilicate glass ceramics with Sr6Ca4(PO4)6F2 nanocrystals were prepared by the controlled crystallization method. The research results of up-conversion (UC) spectra showed that the optimal dopant concentration of Yb3+ and Tm3+ was 3.0 and 0.1 mol%, respectively. In the visible range, the transmissivity of the precursor glass (PG) was close to 90%, while that of glass ceramics was approximately 82%. And the luminescence intensity of glass ceramics was stronger than that of PG. The Rietveld XRD refinement results confirmed that Yb3+ and Tm3+ ions partially entered the Sr6Ca4(PO4)6F2 crystal to form the solid solution. The highest relative sensitivity (Sr-max) of glass ceramics based on thermally coupled energy levels (TCELs) was 2.77% K-1 (@298 K). In view of non-TCELs, the highest absolute sensitivity (Sa-max) of glass ceramics was 12.21% K-1 (@698 K). These findings demonstrate that the as-prepared glass ceramic can be expected to be suitable for optical temperature sensing applications.

Optical temperature sensitivity, up-conversion luminescence and structure of Ca5 (PO4)3F: Yb3+, Ho3+, Tm3+ glass-ceramics

The melt quenching and subsequent controlled crystallization method was used to prepare Yb3+/Ho3+/Tm3+ triple-doped Ca5(PO4)3F glass ceramics (GCs), and the structural, optical property, luminescence and temperature sensitivity characteristics were characterized by structural and spectral analysis. The results show that Ca5(PO4)3F nanoparticles are precipitated in the precursor glass (PG). GC820 sample exhibits Sr−max=1.91% K−1 and Sa−max=0.475‰ K−1 based on thermally coupled emitting state. Meanwhile, according to the non-thermally coupled emitting state, the GC820 specimen displays Sr−max=1.23% K−1 and Sa−max=5.94% K−1. This finding indicates that Ca5(PO4)3F: Yb3+, Ho3+, and Tm3+ GCs are promising materials for optical thermometry.

NaLaMo2O8:Yb3+, Er3+ transparent glass ceramics: Up-conversion luminescence and temperature sensitivity property

A novel transparent Yb3+/Er3+ co-doped NaLaMo2O8 glass ceramics (GCs) with borosilicate glass as the matrix were prepared via glass melting and subsequent controlled crystallization method, and the light transmission property, phase structure, microstructure and up-conversion (UC) performance were characterized by XRD, TEM, transmittance spectroscopy and photoluminescence spectrum. A decrease in the lattice parameter of NaLaMo2O8 in GC sample was verified by XRD Rietveld method, indicating the successful incorporation of Yb3+/Er3+ ions in the Na/La-site of NaLaMo2O8 phase. The UC emission intensity of transparent GCs was significantly enhanced compared to precursor glass. The green light emission in the UC is a three-photon absorption process. The 2.0Yb3+/0.1Er3+(mol%) co-doped GC sample shows the maximum absolute sensitivity of 1.406% K−1 at 473 K, which implies that the as-prepared GC exhibits potential application prospects in the field of optical temperature sensing.

Crystallization behavior, ultrahigh power density and high actual discharge energy density of lead-free borate glass-ceramics containing TiO2

This work presents SrO-BaO-Nb2O5-B2O3-P2O5-K2O-TiO2 glass-ceramics prepared by controlled crystallization method. The uniformly dense microstructure with fine grains can be achieved by introducing TiO2. The structural changes were confirmed by the results of SEM and TEM. The 0.5 mol% TiO2 added glass heated at 750 °C for 2 h demonstrates excellent comprehensive properties of εr= 110, BDS = 1408 kV/cm, high energy storage efficiency (η) of 92% and energy storage density of 9.65 J/cm3. The as-prepared glass-ceramic exhibits ultrahigh power density (86.21 MW/cm3), actual discharge energy density (1.00 J/cm3) and excellent temperature stability. These findings qualify this environment-friendly glass-ceramics as one potential candidate for energy storage applications, especially in high power and pulsed power system field.

Enhanced Aqueous Solubility of the Solid Forms of a BCS Class-II Anti-Tuberculosis Drug, Prothionamide

The second-line anti-tuberculosis (TB) drug prothionamide (PRT) has poor aqueous solubility but high permeability; hence, it belongs to the Biopharmaceutical Classification System (BCS) Class II. We report new solid formsa novel polymorph, 6 molecular complexes, and 11 eutecticsof PRT. The solid forms showed superior aqueous solubility compared to the pristine PRT. The single-crystal and powder X-ray diffraction, thermal, spectroscopic, and microscopic data provide in-depth structural, compositional, stability, and phase correlations in the solid forms. Fast evaporation using a rotary evaporator, a kinetically controlled crystallization method, offers an effective strategy to access the coordinates in the landscape that otherwise remain inaccessible. Identified sets of H-bond donor and acceptor sites on PRT, based on the calculated gas-phase molecular electrostatic potential surfaces, provide an empirical route to screen for coformers. The torsional flexibility enjoyed by the thioamide moiety and the propyl chain introduce diversity in the conformational possibilities for PRT.

Crystallization Control of Ternary‐Cation Perovskite Absorber in Triple‐Mesoscopic Layer for Efficient Solar Cells

AbstractControlling the crystallization of organic–inorganic hybrid perovskite is of vital importance to achieve high performing perovskite solar cells. The growth mechanism of perovskites has been intensively studied in devices with planar structures and traditional structures. However, for the printable mesoscopic perovskite solar cells, it is difficult to study the crystallization mechanism of perovskite owing to the complicated mesoporous structure. Here, a solvent evaporation controlled crystallization method to achieve ideal crystallization in the mesoscopic structure is provided. Combining results of scanning electron microscope and X‐ray diffraction, it is found that adjusting the evaporation rate of solvent can control the crystallization rate of perovskite and a model for the crystallization process during annealing in mesoporous structures is proposed. Finally, a homogeneous pore filling in the mesoscopic structure without any additives is successfully achieved and a stabilized power conversion efficiency of 16.26% using ternary‐cation perovskite absorber is realized. The findings will provide better understanding of perovskite crystallization in printable mesoscopic perovskite solar cells and pave the way for the commercialization of perovskite solar cells.

Enhanced photovoltaic performance and stability of planar perovskite solar cells by introducing dithizone

In the two-step spin-coating method, the crystallization and morphology of PbI2 film are essential for producing highly efficient and stable planar heterojunction (PHJ) perovskite solar cells. In this work, the dithizone (DTZ) molecules were introduced into PbI2 precursor to improve the performance of perovskite films. We found that adding DTZ was an effective method to retard the crystallization of PbI2 film and consequently, produced a high-quality perovskite film with pinhole-free, smoother, and fewer defects surface. Most importantly, the presence of residual DTZ in wet PbI2 film also assisted DMSO to slow down the growth of perovskite grains. By tuning the concentration of DTZ, the power conversion efficiency of the best performed cell has increased to 20.66% with negligible photocurrent hysteresis. Meanwhile, the best DTZ device offer an excellent stability, which retained 97% of the initial PCE after storage in the dark for approximately 24 days. We expect this controlled crystallization method could be further explored and provides a useful strategy to improve the performance of perovskite solar cells.

Wide-range thermometry and up-conversion luminescence of Ca5(PO4)3F:Yb3+/Er3+ transparent glass ceramics

Ca5(PO4)3F:Yb3+/Er3+ glass ceramics (GCs) were successfully manufactured via traditional controlled crystallization method. The structural, optical and up-conversion (UC) illuminant properties were systemically investigated by XRD, TEM, HRTEM, fluorescence spectra and luminescence lifetime measurements. The results show that Ca5(PO4)3F:Yb3+/Er3+ nanocrystals has been precipitated from the precursor glass matrix and the UC luminescence mechanism of PG and GC660 is two-photon process. The enhanced UC emission intensity and extended lifetime of Er3+ is observed in the GCs. Using the temperature dependent fluorescence intensity ratio (FIR) of thermally coupled emitting states (4S3/2, 2H11/2) as thermometric index, Ca5(PO4)3F:Yb3+/Er3+ GCs present wide temperature-sensing range (298–798 K) and high absolute sensitivity (51.9 × 10−4 K−1 at 600 K). This finding suggests that Ca5(PO4)3F:Yb3+/Er3+GC materials are promising in optical temperature measurement field.

Well-defined Na2Zn3[Fe(CN)6]2 nanocrystals as a low-cost and cycle-stable cathode material for Na-ion batteries

Well-defined Na2Zn3[Fe(CN)6]2 nanocrystals (~300 nm) have been fabricated by a facile controlled crystallization method from low-cost precursors at room temperature. By employing [Fe(CN)6]3−/[Fe(CN)6]4− couples as redox centres, this material can realize a theoretical 1Na-storage capacity of 70 mAh g−1, a superior high-rate capability of 20 C and an impressive cycle life of 1000 cycles, offering a low-cost and high-performance alternative cathode for large-scale Na-ion applications.

Crystallization Mechanisms and Energy-Storage Performances in BaO-SrO-Na2O-Nb2O5 Based Glass–Ceramics

The [x BaO, (1 − x) SrO]-Na2O (x = 0.0, 0.2, 0.5, 0.8) niobate-based glass–ceramics were prepared through the controlled crystallization method. Crystallization mechanism, phase structure, dielectric properties, and energy-storage properties were studied by adjusting Ba/Sr ratio. It was found that the surface and internal crystallization occurred simultaneously at first crystallization peak, while surface crystallization occurred at second crystallization peak. With Ba/Sr ratio increasing, dielectric constant increased firstly and then decreased, while dielectric loss firstly decreased and then increased. When x = 0.2, optimal dielectric constant of 88 and dielectric loss of 0.0055 were obtained, which is related to the solid solution phase Sr0.5Ba0.5Nb2O6. Breakdown strength (BDS) showed a behavior of increase before decrease. The highest BDS reaches 1975 kV/cm for x = 0.2, which is attributed to uniform and dense microstructure. Correspondingly, the theoretical energy-storage density was increased up to 15.4 J/cm3. Also, discharged efficiency reaches a high value of 91%. Discharged power density of 0.65 MV/cm3 was obtained for x = 0.2 in the RLC pulsed circuit.

Effects of Precursor Structure and the Content of the SO42- on the Electrochemical Performance of LiNixCoyMn1-x-yO2 Cathode Materials

In the present work, the effects of the SO42- content, the crystal growth pattern, the agglomeration of the primary particle on the electrochemical performance are first studied systematically. The LiNi0.4Co0.2Mn0.4O2 precursors are obtained by the controlled crystallization method by different conditions. But the larger primary particle is not beneficial to its electrochemical performances. All the conclusions show that sample 2 possesses the best electrochemical performances, including high capacity, excellent cycle properties. The initial specific capacity at 1C rate of sample 2 is 145.2 mAh/g operated between 4.3and 2.7 V, and 99.4% capacity is maintained after 50 cycles.

High Emissivity of Ca<sup>2+</sup>/Fe<sup>3+</sup>-Doped LaAlO<sub>3</sub> Based Ceramic Materials

High emissive Ca2+/Fe3+-doped LaAlO3 based ceramic materials were prepared by flame spraying and controlled crystallization method. The phase composition, microstructure, infrared optical properties of Ca2+/Fe3+-doped LaAlO3 based ceramic powders were investigated. The physical mechanism for the significantly enhanced infrared emissivity of LaAlO3 by doping with Ca2+ and Fe3+ was analysized. This high emissive Ca2+/Fe3+-doped LaAlO3 based ceramic materials shows promising applications in high temperature thermal process field to enhance the radiative heat transfer and improve its thermal efficiency.

Crystallization kinetics behavior and dielectric energy storage properties of strontium potassium niobate glass-ceramics with different nucleating agents

A series of strontium potassium niobate (KSN-based) glass-ceramics with different nucleating agents have been prepared by conventional controlled crystallization method. The effects of different nucleating agents on crystallization kinetics behavior, dielectric properties and energy storage performances of glass-ceramics have been investigated. It was found that nucleating agents can improve the reaction rate constant (k) of crystallization, which made the KSN-based glasses crystallize at low temperature. Due to the increase of crystallinity, the dielectric constant rose and the breakdown strength decreased. The maximum theoretical energy storage density of 13.5 J/cm3 was obtained when 3 mol.% CaF2 were added as nucleating agents.

Core-shell structured Li[(Ni0.9Co0.05Al0.05)0.6(Ni0.4Co0.2Mn0.4)0.4]O2 cathode material for high-energy lithium ion batteries

A layer of Ni0.4Co0.2Mn0.4(OH)2 precursor was uniformly deposited on the surface of Ni0.9Co0.05Al0.05(OH)2 particles through a controlled crystallization method. The resulting particles were then homogeneously mixed with LiOH·H2O and subjected to high-temperature calcination at 800 °C under flowing oxygen to yield layered core-shell cathode material Li[(Ni0.9Co0.05Al0.05)0.6(Ni0.4Co0.2Mn0.4)0.4]O2. The elemental compositions in Ni, Co, and Mn of both the core and outer layer of the particles were analyzed by energy dispersive X-ray spectroscopy (EDX), and the data suggested that the core was rich in Ni and the shell in Mn. The shell thickness was estimated to nearly 1 μm, and the average composition of the prepared material was determined as Li(Ni0.7Co0.11Mn0.16Al0.03)O2. In the voltage range of 2.8–4.3 V, the initial discharge capacity and charge-discharge efficiency at 0.1C were estimated to 192.0 mAh g−1 and 91.3% at 25 °C, respectively. After 200 cycles, the retained capacity was calculated as 170.7 mAh g−1 at 1C charge-discharge rate, which was equivalent to 95.8% retention. High-temperature testing at 55 °C evaluated the initial specific discharge capacity at 0.1C to 207.2 mAh g−1, with capacity retention achieving 88.6% after 200 cycles at 1C, showing excellent electrochemical properties.

Super broadband near-infrared luminescence in Ni2 +-Er3 + co-doped transparent glass ceramics

Ni2+-Er3+ co-doped glass ceramics containing ZnGa2O4 nanocrystals were fabricated by in situ controlled crystallization method. The adverse energy transfer between Ni2+ and Er3+ could be suppressed in the ZnGa2O4 glass ceramics. And the super-broadband infrared luminescence with full width at half maximum (FWHM) of about 400nm covering 1.1–1.7μm wavelength region was observed in Ni2+-Er3+ co-doped glass ceramics. The two lifetimes of 1NE-GC950 revealed that two luminescence mechanism involved in the luminescence process, Ni2+: 3T2g (3F)→3A2g (3F) and Er3+: 4I13/2→4I15/2 respectively. Compared to that in the Ni2+/Er3+ co-doped glass ceramic containing γ-Ga2O3 and LaF3 nanocrystals, the nanocrystals in the present paper is just only one, ZnGa2O4 nanocrystals, and it could also present super-broadband luminescence.

Effects of Sr substitution for Ba on dielectric and energy-storage properties of SrO-BaO-K2O-Nb2O5-SiO2 glass-ceramics

In this work, [xSrO, (1−x)BaO]-K2O -Nb2O5-SiO2 (SBKNS, x=0.2, 0.4, 0.6, 0.8) glass-ceramics were synthesized through the controlled crystallization method. The phase structure, dielectric and energy-storage properties were systematically studied through the Sr substitution for Ba. It was found that the dielectric properties were improved due to the formation of solid liquid phase Sr0.5Ba0.5Nb2O6. Breakdown strength firstly increases and then decreases, which strongly depends on the variation in interfacial polarization. The highest value of breakdown strength reaches 1828±88kV/cm for x=0.4, which is attributed to more uniform and dense microstructure and lower interfacial polarization. Correspondingly, the optimized theoretical energy-storage density reaches up to 17.45±0.74J/cm3. The maximum of discharged energy-storage density of 1.45J/cm3 from P-E loop was acquired under electric field of 500kV/cm. Moreover, discharged power density of the capacitor was evaluated and reached a high value of 1.76MV/cm3 in pulsed charged-discharged circuit.

Ni2+-doped new silicate glass-ceramics for broadband near infrared luminescence

The new composite transparent spinel silicate glass–ceramics containing Ni2+-doped ZnGa2O4 and solid solution MgxZn1−xGa2O4 nanocrystals were fabricated by in situ controlled crystallization method. After heat treatment, the crystal phase content of ZnGa2O4 increase with increasing heat treatment temperature, and the Mg2+ ions could enter the crystal lattice of ZnGa2O4 to replace the Zn2+ ions and form a new solid solution MgxZn1−xGa2O4. The coordination environment of Ni2+ was changed from tetrahedral in glasses to octahedral sites in glass ceramics. The super-broadband infrared luminescence with full width at half maximum (FWHM) of about 400 nm overing 1.1–1.7 μm wavelength region and fluorescent lifetime of about 480 μs were observed from the glass ceramics containing MgxZn1−xGa2O4 nanocrystals. It is probably due to the variety of solid solution structure making Ni2+ ions enter two different octahedral sites. At the same time, the impact of heat treatment temperature and the concentration of NiO on peak position and intensity were also discussed. The results demonstrate that the method presented may be an effective way to fabricate super-broadband optical amplifiers and tunable lasers.

Effect of Microwave Processing on the Crystallization and Energy Density of BaO‐Na2O‐Nb2O5‐SiO2‐B2O3 Glass‐Ceramics

Barium sodium niobate (BNN) glass‐ceramics were successfully synthesized through a controlled crystallization method, using both a conventional and a microwave hybrid heating process. The dielectric properties of glass‐ceramics devitrified at different temperatures and conditions were measured. It was found that the dielectric constant increased with higher crystallization temperature, from 750°C to 1000°C, and that growth of the crystalline phase above 900°C was essential to enhancing the relative permittivity and overall energy storage properties of the material. The highest energy storage was found for materials crystallized conventionally at 1000°C with a discharge energy density of 0.13 J/cm3 at a maximum field of 100 kV/cm. Rapid microwave heating was found to not give significant enhancement in dielectric properties, and coarsening of the ferroelectric crystals was found to be critical for higher energy storage.

Spherical Al-substituted ɑ-nickel hydroxide with high tapping density applied in Ni-MH battery

Abstract Spherical Al-substituted ɑ-Ni(OH) 2 with high tapping density are prepared with controlled crystallization method, where the synthesis parameters are previously calculated out according to theoretical analysis. The formation mechanism of Ni(OH) 2 particles is analyzed based on theoretical calculation, the optimal conditions for the formation of spherical Al-substituted ɑ-Ni(OH) 2 with high tapping density are figured out and a formula indicates the restrictions among main synthesis parameters is derived, which is reference meaningful for the synthesis of commercialized electrode powders. Synthesized by using the calculated parameters, the obtained ɑ-Ni(OH) 2 shows uniform spherical morphology, high crystal phase purity and reasonable high tapping density of 1.37 g cm −3 , which demonstrates the feasibility of the derived formula. Since the electrical conductivity of the pure Ni(OH) 2 is quite low, 5 wt% of CoOOH are coated on the ɑ-Ni(OH) 2 surface to improve their electrochemical performances. The synthesized CoOOH coated ɑ-Ni(OH) 2 shows relative high specific capacity of 327 mAh g −1 at 0.1 C and acceptable high-rate dischargeability. The simultaneously achieving of high tapping density and high specific capacity in ɑ-Ni(OH) 2 makes it own the great potential to be applied in new generation of Ni-MH batteries.