KF Flux Research Articles

Growth, crystal structure and IR luminescence of KSrY1-xErx(BO3)2.

A series of novel KSrY1-xErx(BO3)2 (x = 0-1) phosphors that emit near-infrared radiation was synthesized using solid-state methods. Pure Y and Er crystals were grown using a KF flux via the top-seeded solution growth technique. In situ high-temperature single crystal X-ray diffraction, Raman spectroscopy and DFT calculations were used for characterization. Within the series, a polymorphic phase transition from space group P21/m to R3m was discovered between 550 and 600°C. The concentration dependence of the luminescence intensity was measured for the samples. A strong emission of Er3+ electron transition 4I13/2 → 4I15/2 was detected within the 1529-1549 nm range, with the maximum observed for the KSrY0.4Er0.6(BO3)2 composition.

Fluorite-related iridate Pr3IrO7: crystal growth, structure, magnetism, thermodynamic, and optical properties

Spin–orbit coupling in heavy 5d metal oxides, in particular, iridates have received tremendous interest in recent years due to the realization of exotic electronic and magnetic phases. Here, we report the synthesis, structural, magnetic, thermodynamic, and optical properties of the ternary iridate Pr3IrO7. Single crystals of Pr3IrO7 have been grown by the KF flux method. Structural analysis shows that Pr3IrO7 crystallizes in an orthorhombic phase with Cmcm symmetry. The electron energy loss spectroscopy study indicates that Pr is in a 3+ valence state, which implies a 5+ oxidation state of Ir. Magnetization data measured at high and low magnetic fields do not exhibit any bifurcation between M ZFC and M FC , however, a weak hump in M(T) is observed at 10.4 K. The specific heat data reveal two maxima at ∼253 and ∼4.8 K. The optical conductivity spectrum shows 24 infrared-active phonon modes and reveals an insulating behavior with an optical gap of size ∼500 meV. During cooling down, the temperature-dependent reflectivity spectrum reveals eight extra phonon modes below the structural phase transition (∼253 K). An anomaly is observed at around in the temperature evolution of infrared-active mode frequencies suggesting the presence of significant spin–phonon coupling in the system.

P2272Determinants of left ventricular ATP availability measured in vivo and ex vivo in patients with severe aortic stenosis: correlation of creatine kinase activity with LVEF and ATP diffusion distance

Abstract Introduction The transition to systolic failure in severe aortic stenosis (AS) increases mortality. There are currently no reliable markers of transition, and the guideline LVEF <50% threshold for intervention in asymptomatic severe AS does not capture all subjects at increased risk. In animal models, reduced ATP delivery capacity through creatine kinase (CK) is important, with modest increases in CK capacity conferring cardioprotection. ATP may also diffuse (independent of CK) from mitochondria to the contractile site. We have performed the first human study to test whether ATP diffusion distance relates to CK activity and whether CK activity is reduced in low LVEF severe AS. Methods 19 patients with severe AS, LVEF ≥55% (AS-pEF, mean±SD LVEF 63±5%, mean gradient 48±14 mmHg) and 10 with severe AS, LVEF <55% (AS-rEF, LVEF 42±8%, mean gradient 32±11) underwent 31P-MRS for CK rate constant (kf) and phosphocreatine/ATP (PCr/ATP) ratio, and MRI for LV volumes. LV biopsies were taken during AVR and analysed for CK total activity, CK isoforms, total creatine, and citrate synthase (CS) activity. 9 biopsies also underwent serial block face scanning electron microscopy and mitochondria-sarcomere 3D distance distributions were plotted. Results were compared to 24 controls (LVEF 61±4%), of which 4 had LV biopsy (3 severe MS, 1 LA myxoma, MS-pEF). Surgical patients had flow-limiting atheroma excluded with invasive angiography and prior myocardial infarction excluded with late gadolinium enhancement MRI. Results When compared to controls, both CK total activity and CS activity were lower in AS-pEF (by 27% and 23% respectively, both p<0.05, Panels A-B). Although PCr/ATP reduced in AS-pEF (by 20%, p<0.001, panel C), kf (panel D) and CK flux estimated by kf × total creatine were not different. CK-MB expression reduced in AS-pEF (19 vs 27% of total CK, p=0.003), reflecting compensatory increases in CK-MM (p=0.26) and CK-BB (p=0.18) in the face of reduced CK activity. AS-rEF was associated with further reduction in both CK and CS activities (by 32% and 22% respectively, both p<0.05, Panels A-B), but no differences in PCr/ATP, CK kf or relative CK isozyme expression were seen. There were no significant between-group differences in total creatine (Panel E). Overall this suggests that CK reserve and oxidative capacity potentially reduce in pressure overload, with further falls commensurate with systolic dysfunction. When median mitochondria-sarcomere ATP diffusion distances were plotted against CK total activity a strong positive correlation was observed (r=0.86, p=0.003, Panel F). This suggests a compensatory reduction in diffusion distance develops when CK activity falls. Conclusions Transition to failure in severe AS is associated with lower oxidative capacity and maximal ATP delivery capacity through CK. Despite compensatory falls in ATP diffusion distance and altered CK isozyme expression, these changes may underlie susceptibility to EF decline in AS. Acknowledgement/Funding British Heart Foundation Clinical Research Training Fellowship (FS/15/80/31803) and Programme Grant (RG/18/12/34040).

Neural-network classification of cardiac disease from 31P cardiovascular magnetic resonance spectroscopy measures of creatine kinase energy metabolism

BackgroundThe heart’s energy demand per gram of tissue is the body’s highest and creatine kinase (CK) metabolism, its primary energy reserve, is compromised in common heart diseases. Here, neural-network analysis is used to test whether noninvasive phosphorus (31P) cardiovascular magnetic resonance spectroscopy (CMRS) measurements of cardiac adenosine triphosphate (ATP) energy, phosphocreatine (PCr), the first-order CK reaction rate kf, and the rate of ATP synthesis through CK (CK flux), can predict specific human heart disease and clinical severity.MethodsThe data comprised the extant 178 complete sets of PCr and ATP concentrations, kf, and CK flux data from human CMRS studies performed on clinical 1.5 and 3 Tesla scanners. Healthy subjects and patients with nonischemic cardiomyopathy, dilated (DCM) or hypertrophic disease, New York Heart Association (NYHA) class I-IV heart failure (HF), or with anterior myocardial infarction are included. Three-layer neural-networks were created to classify disease and to differentiate DCM, hypertrophy and clinical NYHA class in HF patients using leave-one-out training. Network performance was assessed using ‘confusion matrices’ and ‘area-under-the-curve’ (AUC) analyses of ‘receiver operating curves’. Possible methodological bias and network imbalance were tested by segregating 1.5 and 3 Tesla data, and by data augmentation by random interpolation of nearest neighbors, respectively.ResultsThe network differentiated healthy, HF and non-HF cardiac disease with an overall accuracy of 84% and AUC > 90% for each category using the four CK metabolic parameters, alone. HF patients with DCM, hypertrophy, and different NYHA severity were differentiated with ~ 80% overall accuracy independent of CMRS methodology.ConclusionsWhile sample-size was limited in some sub-classes, a neural network classifier applied to noninvasive cardiac 31P CMRS data, could serve as a metabolic biomarker for common disease types and HF severity with clinically-relevant accuracy. Moreover, the network’s ability to individually classify disease and HF severity using CK metabolism alone, implies an intimate relationship between CK metabolism and disease, with subtle underlying phenotypic differences that enable their differentiation.Trial registrationClinicalTrials.gov Identifier: NCT00181259.

Efficient upconversion luminescence in Er3+/Yb3+ co-doped cubic NaYF4 single crystals by vertical Bridgman method with KF flux

Er3+/Yb3+ co-doped α-NaYF4 single crystals with various Yb3+ concentrations and ∼0.50 mol% Er3+ were grown by Bridgman method using Potassium fluoride as flux. The up-conversion (UC) luminescence and its pump power dependence on UC emission of the crystals under excitation of 980 nm laser diode were investigated. The UC emissions at green ∼522 nm, ∼541 nm and red ∼668 nm, which are attributed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively, were obtained in Er3+/Yb3+ doped α-NaYF4 single crystals. The quadratic dependence of pump power on the UC emission suggests that a two-photon process is responsible for the transition from the excited Yb3+ to the lower state of Er3+ ions in α-NaYF4 single crystals. A favorable performance of yellowish green light can be achieved with certain Yb3+ concentrations and 0.52 mol% Er3+ co-doped samples that makes further research valuable in developing UC displays for electro-optical devices.

ChemInform Abstract: Synthesis, Structure, and Polymorphism of A3LnSi2O7 (A: Na, K; Ln: Sm, Ho, Yb).

AbstractCrystals of K3SmSi2O7 (I) are grown from stoichiometric Sm2O3 and SiO2 in a KF flux (KF‐covered Ag crucible, 900 °C, 12 h).

Growth and downconversion luminescence of Ho3+/Yb3+ codoped α‐NaYF4 single crystals by the Bridgman method using a KF flux

Downconversion (DC) luminescence with emission at about 1000 nm under excitation of 448‐nm light in Ho3+/Yb3+ codoped α‐NaYF4 single crystal is realized. The crystal was grown by the Bridgman method using KF as an assisting flux in a NaF‐YF3 system. The energy‐transfer process and quantum cutting (QC) mechanisms are presented through the analysis of the spectra. The energy‐transfer processes of first‐ and second‐order cooperative DC are responsible for the increase of the emission intensity at 1000 nm, and it is the first‐order cooperative DC that is dominant for the DC process. When the Ho3+ concentration is fixed at about 0.8 mol%, the optimal concentration for ∼1000 nm emission is 3.02 mol% Yb3+ in the current research. The energy‐transfer efficiency and the total quantum efficiency are analyzed through the luminescence decay curves. The maximum quantum cutting efficiency approaches to 184.4% in α‐NaYF4 single crystals of 0.799 mol% Ho3+ and 15.15 mol% Yb3+. However, the emission intensity at 1000 nm decreases while the energy‐transfer efficiency from Ho3+ to Yb3+ increases, which may result from the fluorescence quenching between Ho3+ and Yb3+ ions, Yb3+ and Yb3+ ions.

Synthesis and structure of the new pentanary uranium(vi) silicate, K4CaUSi4O14, a member of a structural family related to fresnoite

Single crystals of K4CaUSi4O14 have been grown from a eutectic CaF2–KF flux. K4CaUSi4O14 crystallizes in a new structure which exhibits a 49-fold superstructure believed to be due to a modulation of the uranium and silicon polyhedra. We report the sub-cell of the structure which adopts the tetragonal space group Pn2 with lattice parameters a = 9.2862(2) Å, c = 8.3796(4) Å, and V = 722.60(5) Å3. K4CaUSi4O14 is a member of a structural family related to the mineral fresnoite which we describe here. Finally, we report UV-vis absorbance and SHG measurements on the compound, which is non-centrosymmetric.

Diffusive behavior of a surface layer in BaTiO3crystals grown by Remeika method

BaTiO 3 crystals, grown by Remeika method, were studied by means of acoustic emission and dielectric response. It is established, that the phase transition in the surface layer occurs on 13 °C below in comparing with the crystals bulk. It is observed, that the imaginary dielectric response of a crystal surface layer exhibits an essential smearing and slight frequency shift to higher temperatures. Reasons of such properties are discussed from a viewpoint of diffusive phase transition, taking place in the surface layer, enriched by K + ions from KF flux.

Growth, characterization and the fourth harmonic generation at 266 nm of K2Al2B2O7 crystals without UV absorptions and Na impurity

We utilize a combined technology to grow relatively pure K2Al2B2O7 crystals without sodium and UV absorptions aroused by Fe3+ ions. It is found that under reducing atmosphere, iron impurities can no longer substitute into the Al3+ sites in the crystal lattice. Thus, the as-grown crystals are free from the abnormal UV absorption from 200nm to 300nm. At the same time, KF flux prevents the inclusion of sodium into the crystal contrasted with the generally used NaF flux. Lattice parameters of the as-grown crystals were refined by powder X-ray diffraction and compared with those grown from NaF flux. Based on the measured refractive indices, new Sellmeier equations were derived from refractive index dispersion curves. Finally, FHG experiment of a QCW Nd:YAG laser at 266nm demonstrated an output power of 440mW, which is the highest record achieved in KABO crystal so far.

KBa7Mg2B14O28F5, a new borate with an unusual heptaborate group and double perovskite unit

A new borate, potassium barium magnesium borate fluoride, KBa(7)Mg(2)B(14)O(28)F(5), with a nominal 7:1 composition of BaB(2)O(4) to KMg(2)F(5), has been found during the growth of BaMgBO(3)F crystals with a KF flux. It crystallized in the space group C2/c and is composed of isolated heptaborate [B(7)O(14)](7-) groups and double perovskite [Mg(2)O(6)F(5)](13-) units.

Closed Recycling Process for Al-Based Composite Materials

Closed recycling process for low-grade scrap of Al-based composite materials was developed. Flux treatment with water-soluble halide is a key technique in this process. In the present work, flux treatment conditions were discussed from the viewpoints of separation and recovery of base material, reinforcement and flux. Optimum separation condition was obtained for the NaCl–KCl–KF flux treatment. The recovered aluminum alloy can be recycled for various usages. The recovered SiC particles cannot be reused as reinforcement because of the coexistence of contamination, therefore it is necessary to eliminate these contaminates or to find the other uses. The recovered flux is reusable with supplemental addition of fluoride.

Growth and properties of K2Al2B2O7 crystal

The flux systems for the growth of crystalline K2Al2B2O7 (KABO) are discussed. KABO can be grown from both KF and NaF flux by a top-seeded growth method. It is easier to grow the crystal in NaF flux than to do so in KF flux. Seed directions influence the quality and morphology of the KABO crystal. The average thermal expansion coefficients are experimentally determined to be 8.4×10−6/K, 1.65×10−5/K along a-axis and c-axis, respectively. The specific heat was measured over a range of temperature 30–295 °C, which is double that of crystalline BBO. Some other data on the chemical and physical properties of KABO are also presented.

Flux growth of perovskite-type RAlO 3 single crystals

Single crystals of RA1O 3 (R = La-Lu) were successfully obtained at atmospheric pressure by a flux method using KF. According to the R element, solute was prepared by three different processes. Single crystals of RA1O 3 (R = Ce, Pr and Tb) were grown in He atmosphere to prevent oxidation, and others were grown in air. Single crystals are transparent cubes. In the case of the growth experiment of NdA1O 3, the solute was prepared from alcoholates and it was very smoothly dissolved in the KF flux. As a result, crystals of NdA1O 3 were grown up to 300–600 μm in size compared with 30–60 μm for other phases. Single crystals of LuAlO 3 were successfully obtained for the first time by this flux method at ambient pressure in air. RA1O 3 for R = La, Pr and Nd shows trigonal symmetry with a rhombohedral lattice, and CeAlO 3 crystallizes in tetragonal symmetry. Others show orthorhombic symmetry. The lattice distortion from an ideal cubic perovskite structure is smaller in the aluminates of rare earth elements with lower atomic numbers in each structure group.

Liquid Phase Epitaxy of Na1−yKyTa1−xNbxO3 for Pyroelectric Applications

ABSTRACTThe epitaxial growth of para- and ferroelectric KTa1−xNbxO3 (KTN) thin films was achieved in an in-house built liquid phase epitaxy (LPE) apparatus. Films were grown from a KF/NaF/KTN solution on KTaO3 substrates. Growth rates of several μ/min were achieved at a growth temperature of 1200 K. Up to 150 μm thick, smooth KTN films with different compositions were grown and characterized. Almost perfect lattice matching was achieved by the addition of NaF to the KF flux. Partial replacement of K by Na did not result in a significant change of physical properties of KTN.The investigation of the dielectric properties revealed a sharp change of the dielectric constant at the ferroelectric phase transition. The ferroelectric domain structure was modified by poling at 1kV/cm. Pyroelectric studies yielded a pyroelectric coefficient of up to 5.2 mC/m2K while the frequency dependence of the pyroelectric response showed a maximum at 230 Hz.

Growth of Gd2SiO5 Crystals from MF (M = Li, Na, and K) Fluxes

Abstract The growth of Gd2SiO5. crystals from MF (M = Li, Na, and K) fluxes was attempted by a slow cooling method. Crystals of Gd2SiO5 were grown from LiF and KF fluxes. Well-formed Gd2SiO5 crystals up to 0.4 mm long were grown from KF flux. Unwanted NaGdSiO4 crystals were grown from NaF flux.

Dielectric relaxation in Fe or Nb doped barium titanate single crystals

Abstract We report several dielectric relaxation measurements in Fe or Nb doped barium titanate grown either in KF flux (Remeika method) or in TiO2 flux (pulling method). The mean field approximation is not valid : the dipoles exhibit a collective effect, perhaps as in a polar glass, but complicated by various compensation mechanisms.

Crystal growth and characterization of two kinds of Fe doped BaTio3 single crystals

Abstract Single BaTio3: Fe crystals are either grown in a KF flux or pulled in a Tio2 Flux; the transition temprature decreases in the same way in the two kinds of crystals. The optical measurements show an apperent reduction of the intrinsic gap. These two phenomena are related to that Fe3+ ions occupy the high symmetry site for Ti-ions, thus modifying the point and translation symmetry.

Optical and electrical properties of Nb doped BaTiO3single crystals grown either by the KF flux or the pulling method

Abstract Electrical and optical properties of two kinds of BaTiO3:Nb crystals are presented and discussed. Among the three pictures (band conduction, small polarons and random electronic effects) the present study supports the first mechanism with the same forbidden band for all the crystals, where optically inactive levels due to impurity and optical transitions inside the conduction band for crystals with Ti3+ ions play an important role.

Electrical properties of Nb doped BaTi03crystal with special emphasis on contact influence.

Abstract Previous (1) and recent (2,3) works have been reported on Nb-doped BaTi03 crystals obtained by various methods. The electrical properties of 1% Nb-doped BaTi03 samples, grown in the Laboratoire des Dielectriques, Universite de Dijon (France), by the KF flux (Remeika method), are reported in the present work. The electrical conductivity is studied: the nature of contacts playing a significant role, two other methods are used to investigate this point.