Synthesis of the Complex Fluoride LiBaF_(3) through a Solvothermal Process

The complex fluoride LiBaF3 is solvothermally synthesized at 180degreesC and characterized by means of X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis and infrared spectroscopy. In the solvothermal process, the solvents, mole ratios of initial mixtures and reaction temperature play important roles in the growth of the single crystal.

Mild Hydrothermal Synthesis and Optical Properties of the Complex Fluoride KMgF_3 Doped with Eu

KMgF3 doped with Eu was synthesized by mild hydrothermal method at 240C for the first time. The excitation and emission spectra of the KMgF3 : Eu2+ phosphor were measured. Comparing with the sample synthesized through solid state reaction, the variation in the excitation spectra at 360 nm resulted from the existences of VK color centers; the low emission intensity was due to Eu2+ having transferred part energy to VK color centers.

Studies on the Transition Emission of Eu^（2＋） Ion in Complex Fluorides Using Neural Network

Quasi-Newton, fully-connected, and feed forward neural network were used to study the correlation between the spectral structure of the Eu2+ ion in complex fluorides and the structures of complex fluorides. The experimental results show that the neural network architecture (number of layers and number of nodes in each layer),the intial weights. and the organization of the data were all important factors affecting the performance of the neural network. The performance of the neural network was enhanced by adapting a test set to monitor the training process. Once trained, the neural network correctly classified 100% of the training set and 96.3% of the test set. These results offer tremendous improvement over previous pattern recognition methods.

REPLACED SITE OF Eu^(2+) ION IN THE COMPLEX FLUORIDES WITH THE PEROVSKITE CRYSTAL STRUCTURE

The replaced site of Eu^(2+) ion is dependent on the electronegativity difference of the cations in complex fluorides.In the mixed fluoride KMgF_3:Eu^(2+),Eu^(2+) ion occupies K^+ site,its emission spectrum is a sharp line and its valence-state is stable.

Structure of [Co(im)6]SiF6：Short Hydrogen Bonds Involving SiF62- Ions

A new complex C（18）H（24）CoF6N（12）Si has been synthesized by the reaction of cobalt（II） fluoride tetrahydrate with imidazole in a glass vessel. SiF62-was generated by in situ reaction of fluoride on silica. This complex has been characterized by different techniques such as elemental analysis, IR studies, magnetic measurements, electronic absorption measurements and single-crystal X-ray structure determination. The crystals are hexagonal in the R-3 space group, with a = 13.225（6）, b = 13.225（6）, c = 12.517（11） A, and g = 120°. In complex [Co（im）6]SiF6, the cobalt atom is six-coordinated to adopt a regular octahedral geometry and the SiF62-ion acts as the counter anion. The crystal displays a network structure and SiF62- bridging hexagram formation by N-（39）···F-Si interactions between imdazole and SiF62-. SiF62-plays an important role in assembling the supramolecular aggregates.

Nanosized complex fluorides based on Eu^(3+) doped Sr_2LnF_7(Ln=La, Gd)

A simple co-precipitation approach taking place between Ln3＋, Sr2＋ cations and F anions, led to the formation of nanocrystalline Eu3＋ doped Sr2LnF7 （Ln-La and Gd） complex fluorides. The reaction was carried out in the presence of polyeth- ylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu3＋ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd3＋ ions to Eu3＋ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction （XRD） and transmission electron microscopy （TEM） measurements were performed. Also FT-IR spectra of the products were re- corded, revealing the presence of PEG molecules on the nanoparticles suN＇ace. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu3＋ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu3＋ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

Hydrothermal and Solvothermal Synthesis of the Complex Fluoride α′-SrAlF_5

The complex fluoride α′ SrAlF 5 has been synthesized through hydrothermal and solvothermal methods under mild conditions. The effects of the molar ratio of starting materials, temperature, reaction time and solvents on the synthesis of α′ SrAlF 5 were discussed. The final products were characterized by XRD and SEM. The rod like shape of α′ SrAlF 5 is shown in SEM images.

Spectral Structures of Eu^(2+) in ABF_4 and A_2SiF_6 (A=Na,K,Rb,Cs)

The phosphors of ABF_4:Eu^(2+)and A_2SiF_6:Eu^(2+)(A=Na,K,Rb,Cs)have been synthesized,and the crystallographic data obtained accord with ASTM.In these materials,the f→f sharp lines emissions of Eu^(2+) were observed.The coordination numbers of Eu^(2+)in both NaBF_4 and Na_2SiF_6 hosts are less than 8.

Effects of fluoride on the removal of cadmium and phosphate by aluminum coagulation

This study focuses on the effects of p H and fluoride at different molar ratios of fluoride to Al（R F：Al） on the removal of cadmium（Cd^（2＋）） and phosphate by Al coagulation. Fluoride at R F：Al≥ 3：1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high R F：Al of 10：1 whereas at lowered R F：Al（i.e., ≤ 6：1）, an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at p H 7 and 8 and that of phosphate at p H 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated R F：Al. The Al fluoride interactions include the formation of Al-F complexes and the adsorption of fluoride onto Al（OH）3 precipitates, i.e., the formation of Al（OH）n F m. Al-F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower p H. Al-F complexes at high R F：Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low R F：Al shows little effect on Al coagulation behavior towards Cd^2＋and phosphate, and the spent defluoridation adsorbent,i.e., aluminum（Al） hydro（oxide） with adsorbed fluoride at R F：Al of below 0.1：1, may be reclaimed as a coagulant after being dissolved.