LaF3 System Research Articles

Low‐temperature phase formation in the SrF2–LaF3 system

AbstractPhase formation in the SrF2–LaF3 system was studied at temperatures ranging from 300°C to 450°C using nitrate flux. The solubility of LaF3 in SrF2 decreases with decreasing temperature. The equilibrium width of the solid solution region Sr1−xLaxF2+x at 400°C, it is 44.6 ± 0.4 mol% LaF3 (x = 0.446), at 350°C — 38.3 ± 0.7 mol% LaF3 (x = 0.383), and decreases almost to zero at 300°C.

Growth of Fluorite Solid Solution Crystals in the Ternary SrF2–BaF2–LaF3 System and Investigation of Their Properties

A series of three-component isostructural fluorite crystals (Sr1–xBax)0.7La0.3F2.3 (sp. gr. $$Fm{\bar {3}}m$$ , 0 ≤ x ≤ 1), the compositions of which belong to the Sr0.7La0.3F2.3–Ba0.7La0.3F2.3 polythermal section in the SrF2–BaF2–LaF3 system, has been grown for the first time by vertical directional crystallization. Optical, mechanical, and electrical properties of three-component (Sr1–xBax)0.7La0.3F2.3 and two-component M0.7La0.3F2.3 (M = Sr or Ba) crystals have been investigated and subjected to comparative analysis. It is shown that all three-component crystals (Sr1–xBax)0.7La0.3F2.3 are promising optical design materials.

Investigation on Crystallization and Optical Properties of Ca1−x La x F2+x Glass-Ceramics

Transparent oxyfluoride glass-ceramics containing Er3+, Yb3+:Ca1−xLaxF2+x nanocrystals, which may have potential applications in the fields of solid-state laser and luminescence, were prepared. Crystallization of Ca1−xLaxF2+x and behavior of Yb3+ and Er3+ during the heat treatment was investigated. Results showed that alumina content had a significant effect on crystallization of Ca1−xLaxF2+x in the SiO2–Al2O3–CaF2–LaF3 system. Due to the size of phase-separated areas, the size of the crystals during the heat treatment did not change significantly. After crystallization of Ca1−xLaxF2+x in the glass, the majority of Er3+ ions incorporated into the Ca1−xLaxF2+x crystals during the heat-treatment process. Time-resolved luminescence of Er3+ ions in the samples around 842 nm showed that the solubility of Er3+ ions in Ca1−xLaxF3 crystals is higher than pure CaF2 crystals. The glass undergoes an enormous phase separation, which keeps the Yb3+ ions within the other separated phase. Therefore, only at high temperatures (790°C) or with a long heat-treatment time (72 h), there is a possibility for Yb3+ ions to be incorporated into the fluorine phase.

Influence of alkaline earth oxides on thermal stability of oxyfluoride glass

A new type of glass from the Na2O–MeO–Al2O3–SiO2–LaF3 system where MeO = MgO, CaO, BaO and SrO has been studied. The aim of the investigation was to determine, by means of thermal techniques (DTA and DSC), the influence of alkaline earth ions additions on its thermal stability and the ability of LaF3 phase to crystallization. The effect of LaF3 crystallization was analyzed in connection with glass composition expressed by the Al2O3/(MeO + Na2O + 3La2F6) ratio varying from 0.4 to 0.8 for the alkaline earth admixtures. The compositions of the glasses have been designed so as to make it possible to define the effect of the charge of the ion modifiers (Na+, Me2+, La3+) on the alumina position in the framework of the glass. Two series of glasses were obtained with a different F− content. The formation of LaF3 depends directly on the strength of the network and can be control by the Al2O3/modifiers ratio as well as the content of fluorine ions. Generally, it can be stated that transparent glass-ceramic with nanocrystallization of LaF3 can be obtained for Al2O3/(Na2O + MeO + 3La2F6) ≤0.6 in the examined glasses. The more the ionicity of the alkaline earth ions the greater the tendency for the crystallization of Me2LaF7 and MeF2. In the glass structure the substitution of oxygen ions by F− ions facilitated the crystallization of LaF3. Simultaneously, it influenced the thermal stability of the aluminosilicate network and induced the crystallization of appropriate silicates during the heat treatment.

Thermal and structural studies of nanocrystallization of oxyfluoride glasses

The influence of fluorine content on the structure and crystallization of oxyfluoride glasses from the Na2O–Al2O3–SiO2–LaF3 system was studied by DTA/DSC, XRD, FTIR and SEM methods. It has been found that the increase in the fluorine content in the structure of oxyfluoride glasses causes the increase of the flexibility of their structure, which inhibits the process of crystallization of the silicate- aluminium matrix. Simultaneously the ability of the glass for LaF3 crystallization, which shows a multistage character, is increasing. Analysis of the local atomic interactions in the structure of glasses has been used to explain the course of the crystallization.

Effect of LaF3 admixture on thermal stability of borosilicate glasses

Oxyfluoride glass-ceramics based on the aluminosilicate glass-matrix with the nano-phase of fluoride is an interesting material for optoelectronics. A new glass from the SiO2–B2O3–Na2O–LaF3 system in which nanocrystallization of LaF3 could be obtained as well is presented.

Solid solution with fluorite structure in the CaF2 ‐ LaF3 system

AbstractThe phase equilibrium of fluorite Ca1−xLaxF2+x solid solutions in the CaF2 ‐ LaF3 system is investigated by means of DTA and X‐ray analysis. The phase diagram of his system is of eutectic type with limited solid solutions with the structure of components. The eutectic coordinates are 1311°C and 58 mole% of LaF3. The saturation line of fluorite solid solution has an anomalous S‐shape. The elementary cell parameter of this solution has been approximated by the parabolic equation a = ao + 0.597x + + 0.134x2, where ao = 5.46295 Å denotes the parameter of CaF2 elementary cell.Both dc/from 20 to 450°C/and ac/from 450 to 600°C/electrical conductivities were measured at concentrations covering almost whole region of the Ca1−xLaxF2+x solid solution formation. They are characterized by increasing conductivity and decreasing activation energy with increasing LaF3 concentrations. In samples with x > 0, 11 an increase of electrical conductivity due to aging was observed.