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Modulating the emissivity of yttria-stabilized zirconia (YSZ) ceramics in the 3–5 μm range through doping and structural adjustments is crucial for their application as high-temperature low-emissivity materials. This study examined YSZ composite ceramics with various levels of lanthanum fluoride (LaF 3) doping, sintered using a high-temperature solid-phase reaction method, to compare their infrared emissivity within the 3–5 μm range. A systematic investigation focused on the effects of the crystal structure and microporous structure evolution on the infrared emissivity of YSZ/LaF 3 composite ceramics. The results revealed that increasing the LaF 3 doping led to lattice expansion and an increase in oxygen vacancies within the YSZ. When the doping limit of La3+ ions is exceeded, La 2 Zr 2 O 7 is formed. At high doping levels, the formation of volatile ZrF 4 was identified as the primary cause of increased porosity of the composite ceramics. Consequently, the emissivity of the composite ceramics in the 3–5 μm range is minimized at a doping level of 3 mol%. For small amounts of doping, this represents the optimal balance between the lattice expansion and oxygen vacancies. However, at higher doping levels, the increased porosity becomes the dominant factor, reducing the emissivity of the composite ceramics. [ABSTRACT FROM AUTHOR]

Eu/Ag-co-doped transparent oxyfluoride glass-ceramics based on LaF 3 have been obtained by melt-quenching followed by structural analysis employing X-ray diffraction and transmission electron microscopy. Absorption spectra showed only Eu3+ ion transitions, irrespective of the presence of silver or the atmosphere used in the preparation. Excitation spectra obtained by collecting luminescence at 437 nm (Eu2+) and 612 nm (Eu3+) indicated the partial reduction of Eu3+ to Eu2+. As a consequence, by tuning the excitation wavelength, a variety of emission spectra are obtained, highlighting the coexistence of Eu2+ and Eu3+ ions, with the emission dominance of the type of ion dependent on the excitation wavelength. The presence of Ag and the atmosphere used during sample preparation affected the intensity of certain emissions, indicating the presence of oxidation-reduction reactions. Chromaticity diagrams illustrating the changes in colour coordinates corresponding to variations in the excitation wavelength showed a range of colours from red to blue, including purple-blue tones. [ABSTRACT FROM AUTHOR]

Nd3+-doped, LaF 3 -based, transparent oxyfluoride glass-ceramics (GCs) containing Ag nanoparticles (NPs) have been prepared by a melt-quenching method. Different Ag-containing precursors were employed, with AgNO 3 as the most suitable for obtaining Ag NPs segregated in the glassy matrix. Transmission electron microscopy and X-ray absorption spectroscopy determined the presence of Ag0 NPs, with higher concentrations in glass-ceramics produced in an inert atmosphere (N 2). The spectral features of emission and excitation spectra, in addition to the different lifetimes of the 4F 3/2 state in the co-doped samples with Ag NPs, demonstrate the incorporation of Nd3+ ions into the LaF 3 nanocrystals. The relative contribution to the emission from Nd3+ in the nanocrystals depends on the Ag concentration and atmosphere. The glass-ceramic co-doped with 0.2 wt% Ag, thermally treated in N 2 , exhibits the highest contribution of emissions attributable to Nd3+ ions in the crystalline phase. The crystalline fraction is similar to that of a Ag-free sample synthesized under analogous conditions. This increase of the luminescence is likely attributable to the enhancement of the local electric field in the LaF 3 nanocrystals due to the presence of Ag0 NPs. [ABSTRACT FROM AUTHOR]

Controllable growth of nanocrystals (NCs) in optical glasses is essential to impart photonic functions for demanded applications. Here, Ce3+-doped KLaF 4 and LaF 3 fluoride NCs are controllably precipitated in a fluorosilicate glass via adjusting the duration and temperature of thermal treatment. The presence of phase separation in the precursor glass (PG) is derived from molecular dynamics (MD) simulations, and serves as the driving factor for the crystallization of fluoride NCs. The phase separation of PG, NCs distribution, microscopic morphology and particle size of NCs precipitated in the nano-glass composites (nano-GCs) are investigated by analytical transmission electron microscopy (TEM). Structural and spectroscopic characterizations confirm the influence of the thermal treatment on the crystalline species in the nano-GCs. The developed nano-GCs exhibit intense X-ray excited luminescence with an excellent linearity with the X-ray dosage and a good thermal stability, making them suitable for radiation detection and medical imaging applications. [ABSTRACT FROM AUTHOR]

MoS 2 -based films are the most widely used solid lubrication materials in the space environment. However, the environmental sensitivity of MoS 2 determines its low lifetime in low-orbit space environments rich in atomic oxygen (AO). To solve this problem, we optimize the film structure by doping with LaF 3 , which has a hexagonal structure and grain refinement properties. The TEM-FIB cross-section visualization illustrates that the LaF 3 doping can further reduce the voids in the film and improve densification, which improves the AO-resistance of the film and maintains excellent tribological properties with a low friction coefficient of 0.017 and a friction life of more than 1.5 × 106 laps after high-flux AO irradiation. [ABSTRACT FROM AUTHOR]

Slow highly charged ions (HCI) were utilized successfully for the formation of various nanostructures in the surfaces of different materials. The creation mechanism of HCI-induced nanostructures was intensively studied in alkali- and alkaline-earth fluorides. Here, we are investigating another type of fluorine-containing ionic crystals of different crystalline and electronic structure, namely lanthanum fluoride, LaF 3. The single crystals were irradiated with slow (eV-keV) highly charged xenon ions from an Electron Beam Ion Trap. After irradiation, the crystals surfaces were investigated by scanning force microscopy. The measured topographic images show nanohillocks emerging from the surface. These nanostructures were observed only after exceeding a well-defined threshold in the potential energy. The role of ion parameters for nanohillocks formation as well as a comparison with results for swift heavy ion irradiations of LaF 3 single crystals are presented. Furthermore, the similarities and differences between LaF 3 and other ionic fluoride crystals, in the creation of surface nanostructures, are discussed. [ABSTRACT FROM AUTHOR]

Zirconium Boride is widely used as thermal protection materials. However, the characteristics of poor oxidation resistance of ZrB 2 at high temperatures limits its applications. In order to improve the anti-oxidation performance of ZrB 2 , a novel method of doping LaF 3 is adopted in present study. In the synthesis process of ZrB 2 via carbothermal reduction method, LaF 3 was introduced to the initial materials. Motivated by the slightly higher formation temperature of ZrB 2 than the melting point of LaF 3 , a liquid glass phase composed of F and La was deposited on the surface of ZrB 2 , which naturally brought in oxygen starvation and contributed to improved oxidation resistance performance. The crystal lattice parameters and the anti-oxidation ability of ZrB 2 are closely dependent on the added LaF 3 content, which can ascribe to La3+/Zr2+ substitution and the amount of glass phase on the surface of ZrB 2. [ABSTRACT FROM AUTHOR]

Electrochemical studies of LaF 3 in molten FLiNaK salt were performed on inert working electrodes. An additional reduction reaction prior to the decomposition of FLiNaK melt was observed when LaF 3 was dissolved in and the reduction product was later recognized as lanthanum metal by SEM analysis. This phenomenon is very surprising and interesting considering the standard reduction potential of La (III) is more cathodic than that of K (I) and Na (I). The present study corrected the previous study [ 1 ] and will provide a new insight on the electrochemical and thermodynamic investigation of other lanthanides in molten FLiNaK salt. [ABSTRACT FROM AUTHOR]

• The Pr:LaF 3 crystals with different doping concentrations were grown by the Bridgman method with the dimension is about Φ20 mm × 30 mm. • The effects of Pr3+ doping concentration on the LaF 3 crystal optical properties were expounded for the first time. • The continuous-wave (cw) deep red laser were obtained with different doping concentrations of Pr:LaF 3 crystals pumped by an blue laser diode for the first time. The crystal compositions, fluorescence lifetimes, polarized absorption and emission spectra, and laser performance were measured with different doping concentrations of Pr:LaF 3 crystals. Moreover, the effects of Pr3+ doping concentration on LaF 3 crystal optical properties were expounded for the first time. The study found that high doping concentration is easy to cause cross-relaxation, which in turn leads to a decrease in the lifetime of the laser upper energy level. And then affects the output efficiency of the visible laser. The laser experiment results confirm that the maximum output power of 176 mW was obtained with Pr:LaF 3 crystal of 0.5 at.% doping concentration, which is higher than output power (71.3 mW) of 1 at.% doping concentration crystal. As we all know, this is the first report about continuous-wave (cw) laser operation with Pr:LaF 3 crystal pumped by an blue laser diode. [ABSTRACT FROM AUTHOR]

The magnetic properties of LaF 3 :1%Pr3+ fluoride nanoparticles were studied in comparison with bulk LaF 3 :1%Pr3+ crystal and microcrystalline powder using EPR and magnetization measurements complemented by XRD and TEM methods. LaF 3 :1%Pr3+ fluoride nanoparticles were synthesized by co-precipitation method and had two morphotypes: nanospheres and nanoplates. Microcrystalline powder was obtained by grinding a bulk LaF 3 :Pr3+ crystal using a pestle and a mortar. We have found the room temperature ferromagnetic-like response in magnetization measurements for nano- and microcrystalline powders whereas no such response was observed for the bulk crystal. We supposed that surface defects play a key role in the observed magnetization dependences on the magnetic field. • LaF 3 :1%Pr3+ nanocrystals were synthesized via the co-precipitation. • LaF 3 :1%Pr3+ microcrystals were prepared by grinding of the bulk crystals. • Magnetization curves show a weak "ferromagnetism" in powder samples. • The EPR spectra of LaF 3 :1%Pr3+ nano- and micro-crystals are studied. • The possible origin of the observed room temperature "ferromagnetism" is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Neutron imaging devices employing a scintillator can be used in various fields, and eutectic crystals can be suitable for the imaging with a fine position resolution of a few hundred micrometers. Since LiF and LaF3 have different refractive indexes of 1.41 and 1.64 at 300nm, respectively, the eutectic crystal is expected to behave as a scintillator with light guiding properties. Thus, the optical properties of Ce-doped LiF/LaF3 eutectic crystal grown by micro-pulling down method were investigated. The light output of LiF/Ce:LaF3 eutectic crystal was relatively small. The emission peaks at 300nm originating from Ce3+ of 5d–4f transition were observed under excitation by UV photons and 5.5MeV alpha rays. Moreover, the photo-luminescence decay time of Ce-doped LiF/LaF3 eutectic crystal was estimated to be 17±1ns. [Copyright &y& Elsevier]

Highlights: [•] The obtained lattice constants of LaF3 are in good agreement with the experimental data. [•] The pressure dependences of elastic constants of LaF3 are investigated for the first time. [•] Calculated band-gap of LaF3 is better than other calculations when compared with experiment. [•] The thermodynamic properties of LaF3 are calculated through quasi-harmonic approximation (QHA) model for the first time. [ABSTRACT FROM AUTHOR]

Abstract: Energy transfer phenomena can play an important role in the development of luminescent materials, and hosts co-doped with Ce3+ and Tb3+ ions continue to be actively studied. Several recent reports on Ce, Tb co-doped phosphors suggest different mechanisms for the energy transfer from Ce3+ to Tb3+ ions and further study is required to reach consensus on the mechanism or to understand why different mechanisms dominate in different hosts. A more direct method of analysis is proposed to distinguish between the different types of multipole energy transfer mechanisms. When applied to Ce, Tb co-doped LaF3, the experimental data shows a poor match to any of these models but is consistent with energy transfer through the exchange mechanism. The decay curves of Ce emission in Ce, Tb co-doped LaF3 were also studied to obtain further insight on the energy transfer mechanism. Although the decrease in lifetime with increasing Tb concentration shows that energy transfer occurs through a non-radiative mechanism, the form of the decay curves does not correspond to what is expected for energy transfer via multipole interactions. [Copyright &y& Elsevier]

Abstract: The method of lanthanum fluoride passivating layer synthesis in the matrix of porous silicon by successive ionic layer deposition was elaborated and optimized. Luminescence and FTIR of obtained structures demonstrate the crucial role of the chemical composition of silicon nanocrystallite surface in the formation of radiative recombination channels and in the stability of porous silicon photoluminescence. The combination of high optical transparency of LaF3 layers and low recombination losses in silicon covered with such layers allows to recommend the lanthanum fluoride film as an effective passivating coating for silicon optoelectronics devices. [Copyright &y& Elsevier]

Abstract: Rare earth doped oxyfluoride glass ceramics with LaF3 nano-crystals formed inside were fabricated for color converter of UV-LED. Among various rare earth ions, Dy3+ and Eu3+ showed practically utilizable visible emissions under UV-LED excitation of 365nm. The visible emission has been improved by the formation of LaF3 brought by heat treatment. X-ray diffraction and transmission electron microscopy along with its energy dispersive spectra confirmed the formation of LaF3 nano-crystals. Compositional dependence and the effects of heat treatment conditions on the visible emissions have been investigated. The CIE chromaticity coordinates of the glasses were also examined for Dy3+ singly doped and co-doped samples. The effect of LaF3 nano-crystals and co-dopants on the visible emission properties of Dy3+ was discussed. [Copyright &y& Elsevier]

Abstract: The cycle performance of spinel LiMn2O4 at 25 and 55°C is improved by LaF3 modification via a chemical deposition method. The physical and electrochemical performances of pristine and LaF3-coated LiMn2O4 cathode materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. The coated LiMn2O4 with 2.92wt% LaF3 (LaF3-3-LMO) displays capacity retentions of 90.1% and 84.2% at 25 and 55°C, respectively, after 100 cycles, much higher than those of pristine LiMn2O4, 72.7% and 54.8%. The concentration of manganese dissolved from LaF3-3-LMO in electrolyte is much lower than that from pristine LiMn2O4. The analysis of AC impedance indicates that the charge transfer resistance (R ct) and the increase of R ct for LaF3-3-LMO during cycling are much lower than those for pristine LiMn2O4. The significantly improved electrochemical performance of the LaF3-coated LiMn2O4 can be attributed to the reduction of manganese dissolution in electrolyte and charge transfer resistance with the help of LaF3 coating. [Copyright &y& Elsevier]

Abstract: Lanthanum fluorides are important materials for their optical properties especially in the form of thin film or nanoparticles. In this paper we describe preparation of LaF3 nanoparticles by simple one-step synthesis. Ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) was used both as fluorination agent and solvent in the first preparation method and KPF6 (fluorination agent) dissolved in ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl) in the second synthesis procedure. In both cases liquid La(NO3)3 was used as the source of lanthanum. Reaction was performed at 200°C for 90min. Obtained white powders were washed by distilled water and methanol, dried on air and analyzed by Nanophox (particle size distribution), X-ray diffraction and by SEM and HRTEM. Nanoparticles of pure LaF3 were prepared and their size was estimated from X-ray pattern to be 11.0 and 11.6nm in the first and second case, respectively. Sizes of nanocrystals were conformed by HRTEM. It was observed by SEM that nanoparticles tend to form irregular aggregates and their average size was estimated by Nanophox. Although nanocrystals prepared by both ways are of very similar size, the sizes of their aggregates differ significantly (730nm from bmimPF6 vs. 3600nm from KPF6 in bmimCl). [Copyright &y& Elsevier]

Abstract: LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals were successfully synthesized using solvothermal method. The crystal structure, morphology and photoluminescence properties of as-prepared nanocrystals were investigated in detail. XRD patterns show that the obtained LaF3:Yb3+,Er3+ core and LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals exhibit hexagonal structure. The average particle size is about 9.3nm and 11.4nm for core and core/shell nanocrystals, respectively. Compared with LaF3:Yb3+,Er3+ nanocrystals, both the upconversion emission intensity and the lifetime increase in LaF3:Yb3+,Er3+/LaF3 core/shell nanocrystals. The enhancement can be attributed to the LaF3 shell which can eliminate the nonradiative centers on the surface of LaF3:Yb3+,Er3+ nanocrystals. [Copyright &y& Elsevier]

Abstract: Local environment of fluorine atoms in the lanthanum oxyfluoride aluminosilicate glasses and glass–ceramics modified by SrO was studied by solid state 19F MAS-NMR spectroscopy and X-ray diffraction. The effect of strontium concentration on the formation of crystalline LaF3 phase was determined, as a function of heat treatment conditions. In all glasses studied, the F–Me(n) (where Me=Sr, La), but no Na–F species were observed. The presence of F–La,Sr(n) units, in which fluorine is coordinated by both lanthanum and strontium, was detected in the glass with higher content of SrO. Supplementary XRD analysis of this series confirmed that an increase of strontium contents leads to the formation of Sr0.69La0.31F2.31 and LaSr2F7, instead of the pure LaF3 only. [Copyright &y& Elsevier]

Abstract: Local environment of fluorine atoms in the lanthanum oxyfluoride aluminosilicate glasses and glass-ceramics modified by alkaline earth oxides, i.e. MgO, CaO and BaO, was studied by solid state 19F MAS-NMR spectroscopy. The effect of the type and concentration of the modifier on the formation of crystalline LaF3 phase was determined, as a function of heat treatment conditions. In all series of glasses studied, the F–Me(n), but no Na–F species were observed. The presence of F–La,Ba(n) units, in which fluorine is coordinated both by lanthanum and barium, was detected in the Ba-glass. Supplementary XRD analysis of this series confirmed that an increase of barium contents leads to the formation of Ba0.3La0.7O0.7F1.3, instead of pure LaF3 only. [Copyright &y& Elsevier]

Abstract: The structure of transparent F-containing nano-crystalline glass-ceramics has been investigated by means of Nuclear Magnetic Resonance as well as X-ray Diffraction as a function of the processing conditions. LaF3 or NaLaF4 are crystallized depending on the glass composition: low silica content and low modifier to alumina ratios lead to crystallization of LaF3, while increasing SiO2 and decreasing Al2O3 results in NaLaF4 nano-crystals. NMR results show that fluorine in glasses is involved in Al–F–Na or La–F environments, the later constituting pre-nucleation sites. After annealing, crystallization of either LaF3 or NaLaF4 crystals takes place, which is correlated with an increase in the intensity of fluorine resonance of La–F environment and a decrease in the Al–F–Na one. The description of the local environment around F, Al and Na is in accordance with a crystallization model of these materials. In low silica containing glasses, it starts from La–F sites and progresses thanks to fluorine diffusion from Al–F–Na bonds until crystal growth is limited through the increase in the viscosity of the glass matrix around crystals. In high silica glasses, long annealing times give rise to crystallization of NaF after NaLaF4 crystals have formed and a silica-enriched region around them inhibits further crystal growth. [Copyright &y& Elsevier]

Abstract: Scintillation from nanoparticles is a nascent field but offers valuable fundamental insights and practical utilities. In this work, the scintillation response of LaF3:Eu nanoparticles is reported. Core/multi-shell nanoparticles were prepared using a modified solution precipitation method that takes advantage of the organic ligand ammonium di-n-octadecyldithiophosphate (ADDP) to simultaneously achieve shelling of doped core nanoparticles while avoiding agglomeration. Nanoparticles were characterized on their structure, morphology, luminescence, and scintillation behavior by means of X-ray diffraction, transmission electron microscopy, photoluminescence, and radioluminescence (RL) measurements, respectively. Analysis of the scintillation process revealed that the unique aspect of scintillation in nanoparticles when compared to bulk materials is related to the migration of carriers within the nanoparticle. Cladding of the Eu-doped core with an undoped shell was found to increase scintillation intensity by a factor of 3, and further shelling leads to a continuous decrease in RL intensity. Surface passivation, together with the decreasing probability of radiative recombination of carriers at the luminescent centers in the core with increasing number of shells grown around the core are suggested to describe the observed RL intensity behavior. Scintillation enhancement by means of shelling is a promising pathway to enhance the use of scintillator nanoparticles in detection devices. [ABSTRACT FROM AUTHOR]

Abstract: Lanthanum fluoride nanoparticles have been synthesized by the simple method of direct precipitation from an aqueous solution. TG/DTA analysis confirms the sample formation at low temperature (300°C). Structure of LaF3 nanoparticles has been analyzed by XRD and LaF3 is found to be in tysonite structure. From the XRD spectra the average particle size is found to be 15nm using the Scherrer formula. The impedance, modulus and dielectric spectra analysis of the prepared LaF3 nanoparticles has been studied using AC impedance spectroscopy. The ionic conductivity of LaF3 nanoparticles is significantly increased by an order from 10−6 to 10−5 Scm−1. The modulus and dielectric spectra analysis confirms the non-Debye type behavior in the material. [Copyright &y& Elsevier]

Abstract: In order to obtain new kind of glass ceramics (with improved mechanical strength, thermal and chemical resistance), oxyfluoride borosilicate (SiO2–B2O3–Na2O–LaF3) glass, containing Pr3+ ions (0.82–0.41wt% Pr2O3), has been melted and then exposed to thermal treatment at 555°C and 620°C. Changes in the absorption and emission spectra and in the fluorescence kinetics are observed and analyzed. In this work we report in detail on the results of measurements along with interpretation which indicate an existence of a nano-crystalline phase in the glass as a result of thermal treatment. [Copyright &y& Elsevier]

Abstract: The effect of alkaline earth ions as a function of composition of oxyfluoride aluminosilicate glass has been explored with FTIR spectroscopy. Glasses have been prepared for Al2O3/(Na2O+MeO+3La2F6) ratio from 0.4 to 0.8 in Na2O–MeO–Al2O3–SiO2–LaF3 systems with CaO, MgO and BaO substitution, respectively. The influence of Me2+ ions on the network structure of melts has been studied. The role of F− replacing O2− ions in the glassy network has been described as well. Spectroscopic results have been compared with thermal stability of glass and tendency to LaF3 ceramization. Finally, the effect of crystallization of LaF3 as a phase of low phonon energy (∼350cm−1) for introduction of alkaline earth ions to the glass has been considered. [Copyright &y& Elsevier]

Abstract: In this paper, the spectroscopic properties of Nd3+ doped transparent oxyfluoride glass ceramics containing LaF3 nano-crystals were systematically studied. The formation and distribution of LaF3 nano-crystals in the glass matrix were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Based on Judd–Ofelt theory, the intensity parameters Ω t (t =2, 4, 6), spontaneous emission probability, radiative lifetime, radiative quantum efficiency, width of the emission line and stimulated emission cross-section of Nd3+ were evaluated. Particularly, the effect of Nd3+ doping level on them was discussed. With the increase of Nd3+ concentration in the glass ceramic, the experimental luminescence lifetime, radiative quantum efficiency and stimulated emission cross-section vary from 353.4μs, 78.3% and 1.86×10−20 cm2 to 214.7μs, 39.9% and 1.52×10−20 cm2, respectively. The comparative study of Nd3+ spectroscopic parameters in different hosts suggests that the investigated glass ceramic system is potentially applicable as laser materials for 1.06μm emission. [Copyright &y& Elsevier]

Abstract: Single crystals of CaF2 and LaF3 were exposed to 30-MeV C60 clusters from the tandem accelerator in Orsay, extending earlier irradiation experiments with monoatomic swift heavy ions to larger energy loss values. The irradiated crystal surfaces were investigated by scanning force microscopy (SFM) in contact mode. Topographic images reveal nanometric hillock-like structures protruding from the surface at each cluster impact site. The hillock diameter and height are analyzed and compared to monoatomic projectiles. [Copyright &y& Elsevier]

Abstract: The main fluorescence branching ratios of 1S0 state in SrAl12O19:Pr3+and LaF3:Pr3+ have been determined by vacuum ultraviolet excitation. The original and modified Judd–Ofelt analyses both with normalized method were applied to the absorption spectra of Pr3+ to get three phenomenological intensity parameters: Ω 2, Ω 4, and Ω 6. They were subsequently employed to calculate the branching ratios and decay times of the Pr3+ 1S0 level in SrAl12O19 and LaF3. The result showed that in both hosts, the modified Judd–Ofelt theory with normalized method provided a better agreement with experimental data than the original one. [Copyright &y& Elsevier]

Abstract: LaF3:Eu3+ nanoparticles were prepared by a simple hydrothermal process at low temperature and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fluorescence spectrum. Well-dispersed nanoparticles with an average size of 30nm and a hexagonal shape were obtained. The influences of reaction temperature and time on the preparation and luminescence of LaF3:Eu3+ nanoparticles were investigated. Luminescent quenching occurred at a much higher concentration (∼25mol%) and stronger luminescent intensity than in bulk LaF3:Eu3+. Fluorescence intensity of the LaF3:Eu3+ nanoparticles varied remarkably with calcination temperatures. It was found that samples without any further calcinations can emit quite strong fluorescence. [Copyright &y& Elsevier]

Abstract: Oxyfluoride glasses from the Na2O–Al2O3–SiO2–LaF3 system were obtained as a potencial materials for optoelectronics. The effect of SiO2 content on the tendency to the nanocrystallization of LaF3 as well as the ceramization of the glassy matrix has been studied. Thermal stability of the glass and crystalline phases formed upon heat treatment were determined by DTA/DSC and XRD methods, respectively. The efect of the glass composition on the crystallizing phases was studied by MIR, FIR and Raman scattering methods. AFM method was used to confirm the structural analysis. [Copyright &y& Elsevier]

Stoichiometric fluoride films have been fabricated by magnetron sputtering of fluoride targets with SF6 at around room temperature. Refractive index (n) and extinction coefficient (k) of the optimal AlF3 film are 1.37 and 6×10-4 at 193 nm, and in case of the optimal LaF3 film, n and k are 1.75 and 9×10-4 at 193 nm. The two-step process, which consists of target pre-fluorination and film deposition, enables LaF3 films to grow with dense and bulky structure. An anti-reflective coating at 193 nm was fabricated, and its reflectance and transmittance are 0.03% and 99.2%, respectively. [Copyright &y& Elsevier]

The lanthanum fluoride thin films has been prepared by means of thermal evaporation method. The XRD analysis shows the formation of polycrystalline hexagonal LaF3. The depth profile X-ray photoelectron spectroscopy (XPS) analysis shows the presence of oxide ions throughout the films. The formation of lanthanum oxyfluoride (LaOF) has been identified. The [O]/[F] ratio has been found to be 0.35 which is higher than the previously reported values of LaF3 film applied for the oxygen sensor. [Copyright &y& Elsevier]

Lanthanum fluoride thin film has been prepared by vacuum thermal evaporation method. The hexagonal-phase LaF3 film has been detected by using glancing angle XRD analysis. The XPS analysis confirms the composition of lanthanum fluoride. The F− ion conduction through the grain and grain boundary has been analyzed using impedance analysis. The modulus spectra reveal the non-Debye nature and the distribution of relaxation times of the film. [Copyright &y& Elsevier]

The friction transfer of polytetrafluoroethylene (PTFE) composites is closely related to their tribological performances. To clarify the effects of LaF 3 /CeF 3 on the friction transfer of PTFE-based composites, the transfer film thickness and coverage were investigated under different loads or speeds. The results show that the addition of LaF 3 /CeF 3 can decrease the transfer film thickness and increase the transfer film coverage to form a thin and uniform transfer film, and the co-filling of LaF 3 and CeF 3 is better in promoting friction transfer of PTFE-based composites than single addition of LaF 3 or CeF 3. The correlation between transfer film and tribological properties was also analyzed, which indicates that the friction transfer is beneficial for improving the tribological properties of PTFE composites. • Effects of LaF 3 /CeF 3 contents, applied loads and sliding speeds on the friction transfer of PTFE-based composites. • Relations between the transfer film thickness, coverage, and the tribological performances of the PTFE-based composites. • LaF 3 /CeF 3 can delay PTFE composites degradation and stabilize transfer film to promote friction transfer. • The co-filling of LaF 3 and CeF 3 can promote friction transfer of PTFE composites better than addition LaF 3 or CeF 3 only. [ABSTRACT FROM AUTHOR]

The optimization of dopant concentration in upconverting nanophosphor is a real problem because of distinct limits defined by surface quenching, energy transfer and cross relaxation phenomenon. In this work, LaF 3 based nanophosphors with different doping concentration of Yb3+ and Tb3+ ions were prepared by coprecipitation route. Particles are formed in spherical shape with narrow size distribution i.e. in ∼50–80 nm range. The volume of LaF 3 unit cell shrinks with the doping of Tb3+ and Yb3+, whereas no variation in its phase were observed. The nanophosphors exhibit characteristics of dual mode spectral emitter. Thus, irrespective of excitation source (i.e. either UV or NIR), the intense green emission at 541 nm was observed. The material LaF 3 with optimized molar doping concentration of 5%Tb3+ and 10%Yb3+ shows intense green emission on excitation with either UV or IR light. The time resolve luminescence emission were studied to explore the probability of involved energy transfer process between two dopant ions. • Physical and luminescence properties of LaF 3 :Tb,Yb nanophosphor, synthesized by coprecipition method, were investigated. • Optimization in dopants concentration was carried out to achieve maximum upconversion emission intensity. • The luminescence emission in visible range was observed in all samples under UV or NIR excitation source. • Time resolved UC emission in nanophosphors were studied to examine the involved energy transfer process between dopant ions. • The possible UC mechanisms involving energy transfer from Yb3+ to Tb3+ ion were demonstrated using energy level diagram. [ABSTRACT FROM AUTHOR]

Abstract: In this work we discuss the reconstructive structural phase transition that single crystals undergo under hydrostatic pressure based upon the fluorine and lanthanum coordination in the trigonal phase. The approximation of the fluorine ions, proposed as cause of the phase transition, is investigated using a static lattice simulation procedure. [Copyright &y& Elsevier]

A novel Nd,Er:LaF 3 laser crystal was successfully grown and analyzed for the first time, to the best of our knowledge. An enhanced ∼2.7 μm emission was observed in Nd,Er:LaF 3 crystal under an 808 nm excitation indicating a promising sensitization function to Er3+ ions by Nd3+ ions. Nd3+ ions also show efficient deactivation effect by lowering the lifetime of the lower energy level (4I 13/2) from 22.60 ms to 4.37 ms with the deactivation efficiency of 80.7%. The fluorescence branching ratio, emission cross-section and measured fluorescence lifetime at 2.7 μm are 28.5%, 1.3 × 10−20 cm2 and 5.48 ms, respectively. No self-termination effect exists in the Nd,Er:LaF 3 crystal. These favorable properties show that Nd,Er:LaF 3 crystal a promising medium for solid-state lasers around 2.7 μm pumped by the 808 nm laser diode. • Intense 2.7 emission from Nd,Er:LaF 3 crystal was recorded under 808 nm LD excitation and analyzed for the first time; • Dual functions – sensitization and deactivation effects of Nd3+ ions to Er3+ ions for the 2.7 emission in low-phonon-energy LaF 3 crystal were discovered and investigated; • The Nd,Er:LaF3 crystal exhibits large emission cross-section (1.3×1020 cm2), long fluorescence lifetime (5.48 ms) and high fluorescence branching ratio (28.5 %) at 2.7 μm; • The energy transfer mechanism between Nd3+ and Er3+ ions in Nd,Er:LaF 3 crystal was demonstrated. [ABSTRACT FROM AUTHOR]

We demonstrated the existence of entangled 4I 9/2 (1) x 4G 5/2 (1) quantum state in a pair of Nd3+ ions due to strong resonance quadrupole – quadrupole interaction between the ions. In doing so, we used narrow line (0.05 Å) tunable pulsed dye laser excitation of a 1% Nd3+: LaF 3 crystal at liquid helium temperatures at the 4I 9/2 (1) → 4G 5/2 (1) transition and measured the site-selective near infrared (NIR) fluorescence spectra of different optical centers (OCs) at the 4F 3/2 (1) → 4I 9/2 (1) transition of Nd3+ with high spectral resolution (0.1 Å); the NIR fluorescence excitation spectra at the 4I 9/2 (1) → 4G 5/2 (1) transition (0.05 Å); and by varying the excitation and detection wavelengths we measured the IR fluorescence kinetics of the selected type of OCs. As a result, we observed inhomogeneous splitting within 30 cm−1 of wavenumbers for the fluorescence spectra at the 4F 3/2 (1) → 4I 9/2 (1) transition, manifested in the presence of numerous narrow inhomogeneously broadened spectral lines of different OCs. We have attributed each spectral line to a different single-site, pair, triple, or quad optical centers via analysis of the 4F 3/2 (1) metastable level fluorescence kinetics decay times. Each type of OCs demonstrates its own specific IR fluorescence excitation spectrum at the 4I 9/2 (1) → 4G 5/2 (1) transition detected in a 1%Nd3+: LaF 3 crystal at 1.6 K. One of the spectral lines of the pair centers (with the frequency 17313.3 cm−1) exhibited the fine splitting with the value of 0.2 cm−1. The shape and the value of fine splitting are explained theoretically assuming that this line corresponds to the excitation of the entangled the 4I 9/2 (1) x 4G 5/2 (1) quantum state of the pair of Nd3+ ions located at short distance, R ~ 4.1 Å. • We observed strong inhomogeneous splitting for the NIR fluorescence spectra of Nd3+ in 1 at.% Nd3+: LaF 3 crystal at 1.6 K • We attributed each spectral line to a different single-site, pair, triple, or quad optical centers. • The spectral line of the pair center exhibited the fine splitting (0.2 cm−1). • The shape and the value of fine splitting are explained theoretically. • We confirmed the entangled 4I 9/2 (1) x 4G 5/2 (1) quantum state in a pair of Nd3+ ions. [ABSTRACT FROM AUTHOR]

Abstract: Large size lanthanum trifluoride (LaF3) single crystals doped with Eu2+ and Ca2+ have been grown by the Bridgman–Stockbarger method. Fluoridization of raw materials was carried out by heating commercial reagent LaF3 at above 1000 °C for 10 h with a flow of HF gas in a resistance furnace. Due to lack of EuF2, EuF3 was reduced with Si in vacuum or nitrogen atmosphere at about 900 °C for 2 h. Cracking was considerably reduced by optimizing the growth conditions, such as a small growth rate of 2–3 mm/h and a [001]-oriented seed. LaF3 single crystal up to 50 mm in diameter and 40 mm in length was obtained. [Copyright &y& Elsevier]