7789-23-3Relevant articles and documents
Investigation of KYF4: Yb, Er // KYF4 nanocrystals - Mechanism of the KYF4 formation
Sch?fer,Ptacek,Hickmann,Prinz,Neumann,Haase
, p. 1914 - 1920 (2009)
This paper presents our investigation of the formation mechanism of cubic phase Yb3+ and Er 3+ doped nanoscale KYF4. We generated Yb, Er doped KYF4 nanoparticles, modified with undoped KYF4 following
Phase transitions in K3AlF6
Abakumov, Artem M.,Rossell, Marta D.,Alekseeva, Anastasiya M.,Vassiliev, Sergey Yu.,Mudrezova, Svetlana N.,Van Tendeloo, Gustaaf,Antipov, Evgeny V.
, p. 421 - 428 (2006)
Phase transitions in the elpasolite-type K3AlF6 complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures T1=132°C, T2=153°C and T3=306°C. The α-K3AlF6 phase is stable below T1 and crystallizes in a monoclinic unit cell with a=18.8588(2)A, b=34.0278(2)A, c=18.9231(1)A, β=90.453(1)° (a=2ac-cc, b=4bc, c=ac+2cc; ac, bc, cc - the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T1 and T2. The γ polymorph is stable in the T2a=36.1229(6)A, b=17.1114(3)A, c=12.0502(3)A (a=3ac-3cc, b=2bc, c=a c+cc) at 250 °C and space group Fddd. Above T 3 the cubic δ polymorph forms with ac=8.5786(4)A at 400 °C and space group Fm3m. The similarity between the K 3AlF6 and K3MoO3F3 compounds is discussed.
Two anhydrous salts of tetrafluoroterephthalic acid (H2tF-BDC): K2tF-BDC and Rb2tF-BDC
Werker, Melanie,Dolfus, Benedikt,Ruschewitz, Uwe
, p. 2487 - 2492 (2013)
Two new anhydrous salts of tetrafluoroterephthalic acid (H 2tF-BDC), namely K2tF-BDC (1) and Rb2tF-BDC (2), were synthesized and structurally characterized. The crystal structure of 1 (I2/m, Z = 2) was solved and refined from X-ray single crystal data. K + (CN = 8) is coordinated by six oxygen atoms of five different tF-BDC2- linkers and two fluorine atoms of two of these linkers, which connect the KO6F2 polyhedra to a 3D network. The crystal structure of 2 (P1, Z = 1) was refined from X-ray powder diffraction data. It crystallizes in a structure type already known from Tl 2tF-BDC. Rb+ (CN = 8) is also coordinated by six oxygen and two fluorine atoms. But six tF-BDC2- linkers are involved in the coordination. Again, a 3D network is formed. Both compounds can be obtained as single-phase samples. They are not porous and stable in air. The thermal stability was investigated by DTA/TG measurements. The decomposition starts at approx. 200°C (1) and 230°C (2). Their good solubility in water makes them interesting starting materials for the synthesis of new MOFs with the perfluorinated linker tF-BDC2-. Copyright
Measurement of absolute rate data for the reaction of atomic potassium, K(4 2S1/2), with CF3Cl, CF2Cl2, CFCl3, CF3Br and SF6 as a function of temperature by time-resolved atomic resonance absorption spectroscopy at λ = 404 nm [k(5 2PJ) ← K(4 2S1/2)]
Husain, David,Lee, Yook Heng
, p. 2325 - 2337 (1987)
We present a kinetic study of the reactions of atomic potassium in its electronic ground state, K(42S1/2), with the molecules CF3Cl, CF2Cl2, CFCl3, CF3Br and SF6. Atomic potassium was generated by pulsed irradiation of potassium halide vapour at elevated temperatures and monitored in the 'single-shot mode' by time-resolved atomic resonance absorption using the Rydberg doublet at λ = 404 nm [K(5 2PJ) ← K(4 2S1/2)]. Absolute rate constants for reaction with these molecules were determined as a function of temperature yielding the following Arrhenius parameters (errors 1σ): A/10-10 cm3 molecules-1 s-1 E/kJ mol-1 CF3Cl 1.1±0.5 13.8±2.5 CF2Cl2 2.1±0.6 5.5±0.5 CFCl3 ca. 1 ca. 0 CF3Br 3.9±0.4 12.3±0.6 SF6 8.4±1.33 12.3±0.9 CF4 exhibited anomalous kinetic behaviour. These results represent the first kinetic measurements, relative or absolute, for these fundamental reactions of atomic potassium. This new set of absolute rate data are compared with analogous results reported hitherto for atomic sodium, Na(3 2S1/2), both alkali-metal atoms exhibiting rapid reactions characterised by small energy barriers and being highly exothermic in character.
Exploration on anion ordering, optical properties and electronic structure in K3WO3F3 elpasolite
Atuchin,Isaenko,Kesler,Lin,Molokeev,Yelisseyev,Zhurkov
, p. 159 - 164 (2012)
Room-temperature modification of potassium oxyfluorotungstate, G2-K 3WO3F3, has been prepared by low-temperature chemical route and single crystal growth. Wide optical transparency range of 0.39.4 μm and forbidden band gap Eg=4.32 eV have been obtained for G2-K3WO3F3 crystal. Meanwhile, its electronic structure has been calculated with the first-principles calculations. The good agreement between the theorectical and experimental results have been achieved. Furthermore, G2-K3WO3F3 is predicted to possess the relatively large nonlinear optical coefficients. 2012 Elsevier Inc.
Wet chemical synthesis of LiBaF3 phosphor
Singh, Vartika S.,Joshi,Moharil
, p. 165 - 168 (2013)
LiBaF3 has great potential applications as X-ray storage phosphor, slow neutron imaging, scintillator, vacuum ultraviolet (VUV) optical lithography, etc. Conventionally, LiBaF3 is prepared by solid state reaction between the constituent fluorides. However, the preparation of phase pure material and especially single crystals is rather tricky due to incongruent melting. For the first time, a wet chemical preparation of rare earth activated LiBaF3 is described here. As precipitated powders containing Ce 3+ or Tb3+ exhibited characteristic luminescence. For observing Eu2+ emission, it was necessary to heat the powders in a reductive atmosphere. It is suggested that phosphors prepared by this method may prove useful in applications like OSL, X-ray imaging, etc. which do not require large single crystals.
The mild hydrothermal synthesis of complex fluorides of AZnF3 (A = Na, K)
Li, Hong,Jia, Zhihong,Shi, Chunshan
, p. 1106 - 1107 (2000)
The complex fluorides of AZnF3 (A = Na, K), which are isostructural with perovskite phases were obtained by the method of hydrothermal synthesis at 160-220 °C. Compared with traditional high-temperature solid-state method, the products were pure and contained lower amount of oxygen.
A novel 18F labelled imidazo-oxazolopyridine derivative as β-amyloid imaging agent: Synthesis and preliminary evaluation
Singh, Shivani,Singh, Sweta,Tiwari, Anjani Kumar,Sharma, Rakesh Kumar,Mathur, Rashi,Kaul, Ankur
, p. 183 - 190 (2018)
Visualization of β-amyloid plaques in brain is pivotal for the diagnosis of Alzheimer’s disease. In the present study, we have designed, synthesized and evaluated an imidazo-oxazolopyridine derivative, 2-[2-(4-fluorophenyl)imidazo[1,2-a]pyridine-6- yl]oxa
Molecular Beam Study of Steric Effects in the Reaction K + HF (v = 1, j = 2) -> KF + H
Hoffmeister, Manfred,Schleysing, Ruediger,Loesch, Hansjuergen
, p. 5441 - 5445 (1987)
HF molecules were optically aligned by use of linearly polarized infrared radiation generated by a color center laser tuned to the R1(l) line of HF.The state-specific integral cross section of the reaction K + HF (v = 1, j = 2) -> KF + H was measured for the two different preparations of the approach geometry which result when the plane of polarization is positioned either parallel (?) or perpendicular (?) to the most probable relative velocity of the reagents.At a translational energy of Etr = 0.46 eV the resulting relative difference of the cross sections (? - ?)/?(? = 1/2(? + ?)) amounts to 17 +/- 5percent.This steric effect decreases with rising Etr and reaches zero near 1.2 eV.The data strongly suggest that the reaction occurs via a collinear transition state.
The crystal structure of α-K3AIF6: Elpasolites and double perovskites with broken corner-sharing connectivity of the octahedral framework
Abakumov, Artem M.,King, Graham,Laurinavichute, Veronika K.,Rozova, Marina G.,Woodward, Patrick M.,Antipov, Evgeny V.
, p. 9336 - 9344 (2009)
The crystal structure of α-K3AIF6 was solved and refined from a combination of powder X-ray and neutron diffraction data (a = 18.8385(3)A, c = 33.9644(6)A, S.G. /41 Z= 80, R P(X-ray) = 0.037, Rp(neutr
