13709-49-4Relevant articles and documents
Synthesis and characterization of mixed fluorides Y1-xCa2+1.5xF7 (-1.33 ≤ x ≤ 1.0)
Achary,Patwe,Tyagi
, p. 2093 - 2100 (1999)
In this paper, we report on the synthesis and characterization of the Y1-xCa2+1.5xF7 (-1.33 ≤ x ≤ 1.0) compounds and the phase equilibria in the CaF2-YF3 system, in the continuation of our earlier studies on Sr and Ba analogues. It was found that the solubility limit of YF3 in the CaF2 lattice is about 33 mol% as compared to about 25 mol% of YF3 in BaF2 and SrF2. The CaF2-YF3 system shows the formation of an ordered cubic superstructure after the solubility limit. A hexagonal tysonite type phase separates out beyond 41 mol% of YF3. A single phasic tysonite type product was obtained at the composition with about 75 mol% of YF3, i.e., Y1.9Ca0.65F7.
An organically templated yttrium fluoride with a 'Super-Diamond' structure
Stephens, Nicholas F.,Lightfoot, Philip
, p. 260 - 264 (2007)
An organically templated yttrium fluoride has been prepared hydrothermally and characterised by X-ray powder diffraction. The crystal structure of [C3N2H12]0.5[Y3F10] may be regarded as a 'Super-Diamond' framework, space group Fdover(3, -) m, a=15.4817(1) A, where each carbon atom site of the diamond structure is replaced by a polyhedral [Y6F8F24/2]2- unit. The basic framework type is isostructural with the known phase (H3O)[Yb3F10]·H2O. The novelty in the present case lies in the use of the organic structure-directing agent 1,3-diaminopropane.
The phase diagram YF3-GdF3
Klimm,Ranieri,Bertram,Baldochi
, p. 676 - 681 (2008)
The binary phase diagram YF3-GdF3 was studied by differential scanning calorimetry (DSC). Yttrium fluoride and gadolinium fluoride show complete miscibility in all three phases (orthorhombic room temperature phase, trigonal or hexagonal high temperature phase, liquid). The transformations between room temperature and high temperature phases are of first order and occur at 1338.6 K (YF3) or 1174.8 K (GdF3). Melting points are 1403.1 K (YF3) or 1525.7 K (GdF3), respectively. The cp (T) curve of GdF3 shows a λ shaped local maximum at 1333 K that might be related to a further solid phase transformation of second order.
Phase equilibria in the system sodium fluoride-yttrium fluoride
Thoma,Hebert,Insley,Weaver
, p. 1005 - 1012 (1963)
A phase diagram of the condensed system NaF-YF3 was constructed from data obtained in cooling-curve and quenching experiments. The number and identity of phases co-existing at equilibrium were determined by use of the X-ray diffractometer and the petrographic microscope. Two compounds, NaF-YF3 and 5NaF-9YF3, were formed from the components. Each compound exists in two polymorphic forms, the high-temperature form in both cases crystallizing from molten mixtures as fluorite-like cubic crystals. The two cubic phases form a continuous solid solution with a maximum melting temperature of 975° at the composition 5NaF-9YF3. Lattice parameters and refractive indices of the solid solution appear to be linear functions of the YF3 content, a = 5.447-5.530 A?., refractive index 1.430-1.470. Pure crystals of NaF·YF3 invert from the fluorite cubic form, on cooling below 691°, to a hexagonal form which is isostructural with β2-Na2ThF6, with lattice constants a = 5.95, c = 3.52 A?. The five primary phase fields below the liquidus were found to be NaF, hexagonal NaF·YF3, NaF·YF3-5NaF·9YF3 ss, and two forms of YF3. Two eutectics occur in association with these primary phases, at 29 and 75 mole% YF3 and at 638 and 947°, respectively. Because of the isomorphism of YF3 with the trifluorides of the rare earths samarium-lutetium and the similarity of their cation sizes, the system NaF-YF3 is predicted to be an approximate model for each of the binary systems SmF3-LuF3 with NaF.
Effect of the fluoride additives on the oxidation of AlN
Zhou, Heping,Qiao, Liang,Fu, Renli
, p. 2427 - 2435 (2002)
The oxidation of AlN powder added by the fluorides at temperatures below 700°C in air was discovered in this study. The obvious onset of oxidation of AlN with cryolite and YF3 additions is below 700°C with the product of α-Al2O3 phase, which usually occurs in single AlN powder above 1100°C. The changes on the weight and the FTIR spectra of the AlN powder fired at temperatures lower than 700°C show that cryolite and YF3 greatly promote the oxidation of AlN powder at these temperatures. Different from the action of cryolite and YF3 powder, CaF2 has no obvious effect on the oxidation of AlN. A possible oxidation process, in part corroborated by FTIR and XRF, was proposed to explain the results in the experiments. The oxidation kinetics of AlN in the presence of cryolite were also discussed at the temperatures ranging from 550 to 700°C from the data of the weight gains in this region. The result shows that the oxidation follows a linear law, which implies a reaction rate-controlled process. The considerably low activation energy of 67 kJ mol-1, which is associated with the quick oxidation and the formation of α-Al2O3 at temperatures below 700°C, was determined from the slope of the line fit.
The Copper Ampoule: A New Reactor for the Solid-State Synthesis of Complex Lanthanide Fluorides
Egger, Philipp,Peters, Nils,Hulliger, Juerg
, p. 152 - 155 (1999)
For the first time, copper ampoules have been used as reactors for the solid-state synthesis of complex lanthanide fluorides under vacuum. The high ductility of copper allows for high-vacuum tight sealing of the ampoules by cold welding. Furthermore, no chemical reactivity of copper toward solid fluorides has been observed. Thus, for an examination in view of optical upconversion properties, the superstructure phases Ba4-xY3+xF17+x(x≈0.08) and Pb4?xY3±xF17±x(x≤0.2) have been synthesized by annealing of mixtures of binary fluorides in evacuated copper ampoules.
Electrical and dielectric investigations of the conduction processes in KY3F10 crystals
Ayala,Oliveira,Gesland,Moreira
, p. 5161 - 5170 (1998)
Dielectric constant and ac and dc electrical conductivity measurements have been performed in single crystals of the flourite compound KY3F10, in the temperature range 100 to 770 K. The dielectric response shows both dipolar and char
Hydrothermal synthesis and white luminescence of Dy3+-Doped NaYF4 microcrystals
Cao, Chunyan,Yang, Hyun Kyoung,Chung, Jong Won,Moon, Byung Kee,Choi, Byung Chun,Jeong, Jung Hyun,Kim, Kwang Ho
, p. 3405 - 3411 (2011)
2 mol% Dy3+-doped NaYF4 microcrystals with different morphologies and crystalline phases have been synthesized through a hydrothermal method without assistance of any surfactant, catalyst, or template by controlling reaction temperatures, reaction time, and molar ratios of reactants. For comparison, the samples were also synthesized by a direct coprecipitation method. The final products were characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence excitation and emission spectra, and luminescent dynamic decay curves. Dy3+ exhibits bright white light under near ultraviolet 350 or 351 nm excitation and the white light was evaluated by chromaticity coordinates. The experimental results suggest that the obtained Dy3+-doped NaYF4 microcrystals have potential applications in white light materials.
Studies on the reaction of ammonium fluoride with lithium carbonate and yttrium oxide
Kowalczyk, Ewa,Diduszko, Ryszard,Kowalczyk, Zbigniew,Leszczynski, Tomasz
, p. 189 - 196 (1995)
The reaction of Y2O3 and Li2CO3 with NH4F to produce LiYF4 was studied by thermogravimetric and X-ray diffraction methods. NH4F reacts easily with Li2CO3 in a one-step exothermic process. Fluorination of yttrium oxide gives first YF3 . 1.5NH3 which decomposes at 300-380°C to YF3 +NH3. This process is exothermic. In the absence of excess NH4F, an amou nt of YOF is produced, in addition to YF3, as a product of the reaction of YF3 and unreacted Y2O3. This reaction is endothermic. In the ternary system NH4F-Li2CO3-Y2O3, the first reacts separately with each of the other two and the resulting mixture of simple yttrium and lithium fluorides is converted into LiYF4 at high temperatures.
Thermodynamics of the lanthanide trifluorides. IV. The heat capacities of gadolinium trifluoride GdF3, lutetium trifluoride LuF3, and yttrium trifluoride YF3 from 5 to 350 deg K
Flotow, Howard E.,O'Hare, P. A. G.
, p. 3046 - 3055 (1981)
The heat capacities of three isostructural trifluorides GdF3, LuF3, and YF3 were determined from 5 to 350 deg K by adiabatic calorimetry.Below 15 deg K GdF3 contained an excess heat capacity contribution over the usual lattice heat capacity; LuF3 and YF3
