Mixture Of KF Research Articles

ChemInform Abstract: On KCrF4.

AbstractSingle crystals of KCrF4 are obtained besides other products by annealing a mixture of KF, CuF2, and CrF3 (Au tube, 750 °C, 60 d).

Über die Kristallstruktur von KSc2 F7 / The Crystal Structure of KSc2 F7

Abstract Single crystals of KSc2F7 have been prepared from a mixture of KF and ScF3 . The samples were investigated by X-ray methods. KSc2F7 crystallizes orthorhombically with a = 10.643(2), b = 6.540(1), c = 4.030(1) Å. These data indicate a close crystallographic connection to the monoclinic unit cell of KIn2F7 [1], But in contrast to KIn2F7 , KSc2 F7 crystallizes in space group No. 65. Cmmm - D19 2h. The R-value for 341 observed independent reflections is 0.060.

Synthesis and the crystal structure of a manganoan fluoromica, K(Mg2.44Mn0.24)Si3.82Mn0.18)O10F2.

Synthesis of a manganoan fluoromica KMg3(Si3.5Mn0.5)O10F2 with Mn in fourfold coordination was tried, utilizing mixtures of KF, MgF2, MgO, SiO2 and MnC2O4 for the starting materials. Mica crystals were obtained below 1150°C after crystallization of manganoan chondrodite (Mg, Mn)5Si2O8(OH, F)2. The X-ray structure analysis revealed that the crystal has a structure of the 1 M mica with cell dimensions of a=5.285(1), b=9.157(1), c=10.190(2)A and β=99.97(2)°, and a chemical composition corresponding to K(Mg2.44Mn0.24)(Si3.82Mn0.18)O10F2. The structure refinement was carried out with the full-matrix least-squares procedure to the final R value of 0.043 for 1131 observed reflections. The (Si, Mn)–Oapical distance is 1.616A and the mean (Si, Mn)–Obasal distance is 1.638A. The mean (Si, Mn)–O distance of 1.632A is longer than the literature value of 1.625A for the mean Si–O distance in the SiO4 tetrahedra by 0.007A, supporting the conclusion that Mn atoms substituted a part of Si4+ ions at the tetrahedral sites in the present experiment. The mean octahedral cation-anion distances are 2.071A for M(1) octahedra and 2.070A for M(2). The tetrahedral rotation angle is 1.73°, and the octahedral flattening angles are 58.4° for M(1) octahedra and 58.3° for M(2).

The crystal structures of germanate micas, KMg2.5Ge4O10F2and KLiMg2Ge4O10F2

The crystals of KMg2.5Ge4010F2 and KLiMg2Ge4O10F2 were synthesized from mixtures of KF, MgF2, MgO and Ge02, and of KF, LiF, MgO and Ge02, respectively. They have structures of the 1M type mica with cell dimensions of a = 5.421(2), b = 9.353(4), c= 10.533(2)Å and β= 100.14(4)° in KMg2.5Ge4O10F2 and a= 5.395(1), b=9.341(2), c = 10.547(1) Å and β = 99.87(2)° in KLiMg2Ge4O10F2. The structures were refined with full-matrix least-squares procedures (R = 0.055; 1413 hkl; KMg2.5Ge4O10F2 and R = 0.038; 1451 hkl; KLiMg2Ge4O10F2). The non-bridging Ge—O distance is 1.702 Å in the former and 1.704 Å in the latter crystals, whereas the mean bridging Ge—O distances are 1.757 Å in both crystals. In KMg2.5Ge4O10F2, the Mg2+ ions are distributed over the two independent octahedral sites with different populations, and the structure corresponds to that of dioctahedral micas. In KLiMg2Ge4O10F2, the Li+ and Mg2+ ions are distributed practically at random. The ditrigonal distortions of the tetrahedral layers are much larger than those of the corresponding silicates owing to the larger size of GeO4 tetrahedra having the tetrahedral rotation angles of 12.9° and 13.5° in KMg2.5Ge4O10F2 and KLiMg2Ge4O10F2, respectively.

The crystal structure of synthetic mica, KMg2.75Si3.5Al0.5O10F2

Crystals of KMg2.75Si3.5Al0.5O10F2 were synthesized from a mixture of KF, MgF2, MgO, Al2O3 and SiO2. They have a structure of the 1M type mica with cell dimensions of a=5.292(1), b=9.164(5), c=10.143(1)A and β=100.07(2)°. The structure was refined with the full-matrix least-squares procedure to the final R value of 0.029 for 1228 observed reflections. The observed distortion of the (Si, Al)O4 tetrahedron is in good agreement with that predicted from the chemical formula of the crystal. The ditrigonal distortion of the tetrahedral sheet is intermediate between those of KMg2.5Si4O10F2 and KMg3Si3AlO10F2, having the tetrahedral rotation angle of 3.63°.

The crystal structure of taeniolite, KLiMg2Si4O10F2

Abstract Taeniolite, KLiMg2Si4O10F2, was synthesized from a mixture of KF, LiF, MgO and SiO2, and the crystal structure was refined with three-dimensional x-ray diffraction data. The crystals are monoclinic (1 M type) with the space group C2/m, a = 5.231(1), b = 9.065(2), c = 10.140(1) Å, β = 99.86(2)°, and Z = 2. Refinements with the full-matrix least-squares procedure gave the final R value of 0.024 for 1303 observed reflections. All the bridging Si–O distances are 1.638(1) Å, whereas the nonbridging one is 1.586(1) Å. A comparison of several 1 M-type micas clearly indicates the effect of octahedral cations on the distortion of (Si,Al)O4 tetrahedra. Li+ ions are more concentrated at the M(2) site than at M(1) in conformity with the size difference between the coordination octahedra. The ditrigonal distortion of the tetrahedral sheets is still smaller than that of KMg2.5Si4O10F2, having the tetrahedral rotation angle α of 1.08°. The octahedral flattening angles, ψ are 57.8° and 57.9° for M(1) and M(2) sites, respectively.

Growth of large K 2MnF 4 single crystals and characterization by X-ray and neutron diffraction investigations

Single crystals of K 2MnF 4 up to 100 mm 3 were grown by the Bridgman method using a mixture of KF and 35 mol% KMnF 3. To characterize these large crystals, neutron diffraction investigations were carried out. In agreement with X-ray diffraction measurements the layer type crystal structure of K 2MnF 4 was found to have a significant anisotropy of the mosaic spread.

Electron-diffraction investigation of the molecular structure of potassium fluoroberyllate

exist in the literature [2-6]. The existence of molecules of the composition MIBeF3 in the vapor phase is mentioned in all these works. Thus, a detailed mass-spectrometr ic investigation of the system NaF-BeF 2 [6] showed that there exists a molecule with the composition NaBeg a in the vapor at ll00~ along with other components of lesser percentage when the composition of the condensed phase is 30 mole % BeF 2. We attempted to investigate the vapors of this system by electron-diffrac tion at 1300-1400~ corresponding to a condensed phase of this composition. It was found from an interpretation of the electron-diffrac tion patterns that the BeF 3 fragment has a right triangular structure with the Be atom in the center and with a value for r(Be-F) = 1.49 %. However, our attempt to ascertain the location of the Na atom in the molecule from the electron-diffrac tion patterns we obtained were not successful, which is possibly explained by the presence of other components with considerable dispersibility under the conditions of the electron-diffrac tion experiment. In order to ascertain the location of the alkali metal atom in a molecule of the type MIBeFa, we investigated the structure ofKBeF 3 in this work. By analogy with the NaF-BeF2 system, a composition of the condensed phase for the KF-BeF2 system containing 33 mole % of BeF2 was used to carry out the experiments. Preliminary experiments had shown that the electxon-diffrac tion patterns of the vapors obtained for the composition of the solid phase taken above differ from the electron-diffrac tion patterffs of the starting components of the system and could not be interpreted as the electron-diffrac tion patterns of a simple mixture of KF and BeF z vapors, The work was carried out on an electron-diffrac tion camera designed for investigating difficult-to-vol atilize compounds using the secmr-microphoto metrie method of exposing and treating the electron-diffrac tion patterns. A fusion of the substances was volatilized from a nickel ampule at 1000-1100~ the outflow of the vapor was in the direction of the electron beam. After each exposure, the ampule was carefully fired until the remainder of the salts was completely eliminated, and it was again charged with the initial fusion. The exposures were carried out atvoltages of 40 and 60 kV at a nozzle-to-plate distance of about 515 ram. Elimination of the molecular component of the scattering intensity sM(s) was carried out using a B~SM-4 computer according to a special program [7] while accounting for any correction in the sector function. An analysis of the experimental data obtained was carried out by the least squares method with successive refinement of the parameters as applied to the sM(s) curve. The initial approximation for the parameters was obtained from the radial distribution curve. The initial values of the parameters were refined on the basis of three variants of a model of the KBeF 3 molecule, namely those based on the triangular BeF 3 fragment with the K atom arranged as foIIows:

Optical Study of Lead Zirconate-Titanate

Single crystals of the lead zirconate-titanate solid solution containing 85 percent and those containing less than 40 percent of lead zirconate have been prepared from a molten solvent of a mixture of KF and PbF 2 , and the measurements of optical birefringence have been made. They are all optically negative. The absolute value of birefringence of the crystal containing less than 20 percent of PbZrO 3 shows a maximum when plotted against temperature and resembles the behavior of PbTiO 3 . Such an anomalous behavior tends to vanish with increasing amount of PbZrO 3 . These phenomena are explained taking account of the effect of covalent bonding, after the method developed by Kobayashi and Yamada. 1) The contribution of the covalent nature increases at first and then decreases gradually with increasing PbZrO 3 content. The crystal containing 85 percent of PbZrO 3 is in rhombohedral phase and has larger anisotropy than in tetragonal phase.