Preparation and magnetic properties of TbF3 containing oxide fluoride glasses

New glasses containing TbF₃ have been prepared in a TbF₃-BaF₂-AlF₃-GeO₂ system. Their respective densities, refractive indexes, and glass transition temperatures are (5.42-6.07) × 10³ kg m⁻³, 1.72-1.73, and 605.1-675.2 °C. Their magnetic susceptibilities are proportional to the contents of TbF₃ in glasses obtained in this study. The values agree with the calculated values. The Curie constant of the 40TbF₃-20BaF₂-10AlF₃-20GeO₂ glass is 5.13 K emu mol⁻¹; its effective magnetic susceptibility is 9.96μ_B. The atomic percentage of Tb³⁺ in the 40TbF₃-20BaF₂-10AlF₃-20GeO₂ glass is 11%, which is comparable to that of the oxide glass, which is reported as the material for Faraday components.     

Preparation and optical properties of CeF3-containing oxide fluoride glasses

Cerium-containing oxide fluoride glasses CeF₃-BaF₂-AlF₃-SiO₂ were prepared under CO and Ar atmospheres. The glass prepared in a CO atmosphere exhibited blue emission under UV irradiation because the hydrolysis of CeF₃ to a Ce⁴⁺-containing compound during heating process was controlled. The emission spectrum was separable into three peak components by peak analysis. X-ray photoelectron spectroscopy (XPS) spectra were measured to investigate the valency of the elements in the glass. Oxide and fluoride ions in the glass respectively have different electronic states from those in CeO₂ and CeF₃. The electronic state of cerium ion in the oxide fluoride glass differed from that in CeO₂ and CeF₃.     

InF<Subscript>3</Subscript>-based bismuth-containing glasses

Glasses have been prepared in the InF₃-BiF₃-BaF₂-PbF₂-ZnF₂-LnF₃ (Ln = Eu, Tm) system. The short-range and medium-range order structure of the glass network is discussed on the basis of IR and Raman spectroscopy data. The effect of bismuth trifluoride on the thermal properties, structure, and photo-luminescence properties of glasses was studied. Bismuth trifluoride doping improves the thermal parameters of glasses. The polyhedra formed by bismuth trifluoride in the glass are not involved in the medium-range order. In rare-earth-containing glasses, strong photoluminescence was discovered in the range 530–560 nm with excitation by the Raman-masking 532-nm wavelength. Bismuth in the glass enhances the europium photoluminescence level in the glass of the InF₃-BiF₃-BaF₂-PbF₂-ZnF₂-EuF₃ system.     

Electronic polarizability and crystallization of K2O-TiO2-GeO2 glasses with high TiO2 contents

Some K₂O-TiO₂-GeO₂ glasses with a large amount of TiO₂ contents (15-25 mol%) such as 25K₂O-25TiO₂-50GeO₂ have been prepared, and their electronic polarizability, Raman scattering spectra, and crystallization behavior are examined to clarify thermal properties and structure of the glasses and to develop new nonlinear optical crystallized glasses. It is proposed that the glasses consist of the network of TiO₆ and GeO₄ polyhedra. The glasses show large optical basicities of Λ=0.88-0.92, indicating the high polarizabity of TiO_n (n=4-6) polyhedra in the glasses. K₂TiGe₃O₉ crystals are formed through crystallization in all glasses prepared in the present study. In particular, 20K₂O-20TiO₂-60GeO₂ glass shows bulk crystallization and 18K₂O-18TiO₂-64GeO₂ glass exhibits surface crystallization giving the c-axis orientation. The crystallized glasses show second harmonic generations (SHGs), and it is suggested that the distortion of TiO₆ octahedra in K₂TiGe₃O₉ crystals induces SHGs.     

Transparent oxyfluoride glass ceramics co-doped with Er and Yb - Crystallization and upconversion spectroscopy

Transparent glass ceramics in the system SiO₂-B₂O₃-PbO-CdO-PbF₂-CdF₂-YbF₃-ErF₃ showing infrared to visible anti-Stokes (upconversion) luminescence are studied in the present work. The glass compositions have been optimized in order to reduce the melting temperature and, hence, to obtain laboratory scale samples with good optical quality. Erbium-doped nanoscale Pb₄Yb₃F₁₇ crystals are precipitated in the precursor glasses during annealing at temperatures 30-40 K above T_g. A kinetically self-constrained growth explains the nano sizes of the crystals. Both the Stokes and anti-Stokes luminescence spectra of glasses could be explained with clustering of the Yb³⁺ and Er³⁺ ions in fluorine-rich regions. At the annealing temperature these regions act as nucleation precursors. The crystal growth further enhances the local concentration of these ions. Consequently, a series of energy transfer and energy cross relaxation processes occurs between adjacent rare earth ions leading to the observed luminescence spectra of the glass ceramics studied.     

Enthalpy of mixing in 0.8[xB2O3-(1 − x)SiO2]-0.2K2O melts at 973 K

0.8[xB₂O₃-(1 − x)SiO₂]-0.2K₂O (with 0 ≤ x ≤ 1) glasses were synthesized by melt quenching techniques. DSC curves of the glasses exhibit only one glass transition. Calorimetric measurements of heats of dissolution in lead borate at 973 K indicated small negative enthalpies of mixing. Consequently phase separation was not observed over the whole composition range. The results are in good agreement with the structural data available in the literature.     

Reaction between rare earth elements and HFNO2 solution

Rare earth elements react with HFNO₂ solution to produce nitrosylium fluorometallates (NO)_xLnF_x+3. The value of x is 1.0 or 1.5 for light rare earth elements and 0.5 or 1.0 for heavy rare earths. Nitrosylium fluorometallates of rare earth elements can be decomposed into the simple fluoride and nitrosyl fluoride at low temperatures (46–68°C).     

Thermal and structural analysis of germanate glass and thin films co-doped with silver nanoparticles and rare earth ions with insights from visible and Raman spectroscopy

This paper reports on the thermal and optical properties of germanate glasses GeO₂–PbO co-doped with silver nanoparticles and rare earth ions (Tm³⁺, Er³⁺ and Yb³⁺) with a focus on the thermal diffusivity (D). The presence of rare earth ions and nanoparticles is evidenced by absorption spectra and TEM images, respectively. Additionally, a structural comparison between thin films and bulk glass with the same nominal composition is given. It is found that D increases up to 20% in samples where nanoparticles are present, although their quantity corresponds only to a volume fraction of 1.7%. Therefore, such enhancement could be associated with the nanoparticles. Nevertheless, a Raman analysis revealed a structural change after the thermal treatment used for the nucleation of the nanoparticles. A decrease in the intensity of the band at 534 cm⁻¹ in the Raman spectra is interpreted as the disruption of the 3-membered rings of the GeO₄ tetrahedra. The Raman analysis also revealed the formation of small crystals of α-GeO₂ type quartz and the adsorption of carbon dioxide on the surface of the silver nanoparticles inserted in the germanate thin film.     

Synthesis of nanocrystals in KNb(Ge,Si)O5 glasses and chemical etching of nanocrystallized glass fibers

The nanocrystallization behavior of 25K₂O−25Nb₂O₅-(50−x)GeO₂-xSiO₂ glasses with x=0,25,and50 (i.e., KNb(Ge,Si)O₅ glasses) and the chemical etching behavior of transparent nanocrystallized glass fibers have been examined. All glasses show nanocrystallization, and the degree of transparency of the glasses studied depends on the heat treatment temperature. Transparent nanocrystallized glasses can be obtained if the glasses are heat treated at the first crystallization peak temperature. Transparent nanocrystallized glass fibers with a diameter of about 100 μm in 25K₂O-25Nb₂O₅-50GeO₂ are fabricated, and fibers with sharpened tips (e.g., the taper length is about 450 μm and the tip angle is about 12°) are obtained using a meniscus chemical etching method, in which etching solutions of 10 wt%-HF/hexane and 10 M-NaOH/hexane are used. Although the tip (aperture size) has not a nanoscaled size, the present study suggests that KNb(Ge,Si)O₅ nanocrystallized glass fibers have a potential for new near-field optical fiber probes with high refractive indices of around n=1.8 and high dielectric constants of around ε=58 (1 kHz, room temperature).     

Third- and second-order optical nonlinearity of Ge-Ga-S-PbI2 chalcohalide glasses

Two series of metal iodide doped chalcohalide glasses (100−2x)GeS₂·xGa₂S₃·xPbI₂ (0?x?20) and (100−x)(0.8GeS₂·0.2Ga₂S₃)·xPbI₂ (0?x?15) were prepared and characterized. The microstructure of these glasses has been studied by Raman scattering spectra. Utilizing femtosecond time-resolved optical Kerr effect (OKE) technique at the wavelength of 820 nm, a largest third-order nonlinearity χ⁽³⁾ of 2.07×10⁻¹³ esu was obtained for the 90GeS₂·5Ga₂S₃·5PbI₂ glass, and it decreases with the addition of PbI₂ in both two series. After thermally poled, second-harmonic generation (SHG) has been observed in these glasses according to Maker fringe method and a large second-order nonlinearity χ⁽²⁾ as well as 4 pm/V was obtained for the 70GeS₂·15Ga₂S₃·15PbI₂ glass. The variations of χ⁽²⁾ and χ⁽³⁾ on glass composition are ascribed to the evolution of micro-structural units in glass. These novel chalcohalide glasses would be expected to be the promising candidate materials for nonlinear optical devices.     

Influence of SiO2 on the structure and optical properties of lithium bismuth silicate glasses

Bismuth silicate glasses containing lithium oxide with composition 20Li₂O·(80 − x)Bi₂O₃·xSiO₂ (5 ? x ? 70 mol%) have been prepared by melt-quench technique. Density (D), molar volume (V_M) and glass transition temperature (T_g) for all the glass samples have been measured. FTIR spectroscopy has been employed to investigate the structure of these glasses in order to obtain information about the competitive role of Bi₂O₃ and SiO₂ in the formation of glass network. The increase of SiO₂ content in the glass matrix results in increasing the Si-O-Si bond angle and hence the ionicity of Si-O bond increases with decrease in Bi₂O₃/SiO₂ ratio. The optical transmittance spectra of all the glasses have been recorded in the wavelength range 200-3300 nm. The values of optical band gap (E_g) have been determined from the cutoff wavelength of these glasses. The average electronic polarizability of oxide ion () and the optical basicity (Λ_th) have been estimated from the calculated values of the E_g and were found to be dependent directly on Bi₂O₃/SiO₂ ratio. The variation in different physical parameters such as D, V_M and T_g and optical parameters; viz., E_g, , Λ_th with Bi₂O₃/SiO₂ ratio have been analyzed and discussed in terms of change in the glass structure.     

Spatially selected synthesis of LaF3 and Er-doped CaF2 crystals in oxyfluoride glasses by laser-induced crystallization

Oxyfluoride glasses with a small amount of NiO are prepared using a conventional melt quenching technique, and the spatially selected crystallization of LaF₃ and CaF₂ crystals is induced on the glass surface by irradiations of continuous wave lasers with a wavelength of λ=1064 or 1080 nm. Dots and lines including LaF₃ crystals are patterned by heat-assisted (300 °C) laser irradiations (λ=1064 nm) with a power of P=1 W and an irradiation time of 10 s for dots and a scanning speed of S=5 μm/s for lines. Lines consisting of CaF₂ crystals are also patterned in an ErF₃-doped oxyfluoride glass by laser irradiations (λ=1080 nm) with a power of P=1.7 W and a scanning speed of S=2 μm/s, and the incorporation of Er³⁺ ions into CaF₂ crystals is confirmed from micro-photoluminescence spectrum measurements. It is proposed that the lines patterned by laser irradiations in this study are consisted of the composite of LaF₃ or CaF₂ nanocrystals and SiO₂-based oxide glassy phase. It is demonstrated that a combination of Ni²⁺-dopings and laser irradiations is effective in spatially selected local crystallizations of fluorides in oxyfluoride glasses.     

Approach to thermal properties and electronic polarizability from average single bond strength in ZnOBi2O3B2O3 glasses

The glass transition temperature (T_g), density, refractive index, Raman scattering spectra, and X-ray photoelectron spectra (XPS) for xZnO-yBi₂O₃-zB₂O₃ glasses (x=10-65, y=10-50, z=25-60 mol%) are measured to clarify the bonding and structure features of the glasses with large amounts of ZnO. The average electronic polarizability of oxide ions (α_O2−) and optical basicity (Λ) of the glasses estimated using Lorentz-Lorenz equation increase with increasing ZnO or Bi₂O₃ content, giving the values of α_O2−=1.963 Å³ and Λ=0.819 for 60ZnO-10Bi₂O₃-30B₂O₃ glass. The formation of BOBi and BOZn bridging bonds in the glass structure is suggested from Raman and XPS spectra. The average single bond strength (B_MO) proposed by Dimitrov and Komatsu is applied to the glasses and is calculated using single bond strengths of 150.6 kJ/mol for ZnO bonds in ZnO₄ groups, 102.5 kJ/mol for BiO bonds in BiO₆ groups, 498 kJ/mol for BO bonds in BO₃ groups, and 373 kJ/mol for BO bonds in BO₄ groups. Good correlations are observed between T_g and B_MO, Λ and B_MO, and T_g and Λ, proposing that the average single bond strength is a good parameter for understanding thermal and optical properties of ZnOBi₂O₃B₂O₃ glasses.     

The effects of substituents,molecular symmetry,ionic radius of the rare earth metal,and macrocycle on the electronic absorption spectra characteristics of sandwich-type bis(phthalocyaninato) and mixed (phthalocyaninato)(porphyrinato) rare earth complexes

The electronic absorption spectroscopic data for two series of 60 unsubstituted/substituted bis(phthalocyaninato) and mixed [tetrakis(4-chlorophenyl)porphyrinato](phthalocyaninato) rare earth complexes M(Pc)₂, M(Pc^∗)₂ and M(TClPP)(Pc) [M = Y, La…Lu except Pm; Pc^∗ = dianion of 2,3,9,10,16,17,23,24-octakis(4-methoxyphenoxy)phthalocyanine [Pc(MeOPhO)₈], dianion of 3(4),12(13),21(22),30(31)-tetra(tert-butyl)phthalocyanine (TBPc) and TClPP = tetra(4-chloro)phenylporphyrin] have been measured in CHCl₃. In this paper, the influence of the symmetry of macrocycle rare earth molecules, the effects of ionic radius of the rare earth metal and the influence of substituent species (tert-butyl and 4-methoxyphenoxy groups) onto the peripheral benzene rings on the electronic absorption characteristics of sandwich-type compounds have also been tentatively studied in detail.     

Chemical state analysis of fluorine in various compounds using X-ray fluorescence spectra

F Kα X-ray fluorescence (XRF) spectra of various fluorides were measured and to investigate the chemical state of fluorine in xHoF₃-20BaF₂-10AlF₃-(70 − x)GeO₂ (mol%, x = 10-50) glass. The main peak (Kα_1,2) position and the relative intensity of the satellite peak attributable to Kα_3,4 were discussed relating to the M-F bond covalency. Results showed that the fluorine in xHoF₃-20BaF₂-10AlF₃-(70 − x)GeO₂ (mol%, x = 10-50) glass had a completely different chemical state from that of starting materials. Quantitative analyses of the glasses were also undertaken using XRF measurements for each component. These results suggest that 30% fluorine in the 50HoF₃-20BaF₂-10AlF₃-20GeO₂ system is substituted by oxygen through pyrohydrolysis of the fluorides.     

IRRS, UV-Vis-NIR absorption and photoluminescence upconversion in Ho-doped oxyfluorophosphate glasses

Infrared reflection spectroscopic (IRRS), ultraviolet-visible-near infrared (UV-Vis-NIR) absorption and photoluminescence upconversion properties with special emphasis on the spectrochemistry of the oxyfluorophosphate (oxide incorporated fluorophosphates) glasses of the Ba(PO₃)₂-AlF₃-CaF₂-SrF₂-MgF₂-Ho₂O₃ system have been studied with different concentrations (0.1, 0.3 and 1.0 mol%) of Ho₂O₃. IRRS spectral band position and intensity of Ho³⁺ ion doped oxyfluorophosphate glasses have been discussed in terms of reduced mass and force constant. UV-Vis-NIR absorption band position has been justified with quantitative calculation of nephelauxetic parameter and covalent bonding characteristics of the host. NIR to visible upconversion has been investigated by exciting at 892 nm at room temperature. Three upconverted bands originated from the ⁵F₃→⁵I₈, (⁵S₂, ⁵F₄)→⁵I₈ and ⁵F₅→⁵I₈ transitions have found to be centered at 491 nm (blue, medium), 543 nm (green, very strong) and 658 nm (red, weak), respectively. These bands have been justified from the evaluation of the absorption, normal (down conversion) fluorescence and excitation spectra. The upconversion processes have been explained by the excited state absorption (ESA), energy transfer (ET) and cross relaxation (CR) mechanisms involving population of the metastable (storage) energy levels by multiphonon deexcitation effect. It is evident from the IRRS study that the upconversion phenomena are expedited by the low multiphonon relaxation rate in oxyfluorophosphate glasses owing to their high intense low phonon energy (∼600 cm⁻¹) which is very close to that of fluoride glasses (500-600 cm⁻¹).     

Evidence of network demixing in GeS2-Ga2S3 chalcogenide glasses: A phase transformation study

The information of phase transformation is attained by in situ XRD experiments leading to the knowledge of topological threshold in GeS₂-Ga₂S₃ glasses. The turning point of phase transformation behavior is demonstrated to be glasses containing 14-15 mol% Ga₂S₃. To interpret it a network demixing model is further improved and proposed for the structure of these ternary or quasi-binary chalcogenide glasses. For the nearest-neighbor coordination environment of glass with a transitional composition of 85.7 mol% (6/7) GeS₂·14.3 mol% (1/7) Ga₂S₃, six-coordinated [S₃Ga-X-GaS₃] units (X=S or None) are well isolated by the [GeS₄] structures, which contributes to the decreasing of precipitation of Ga₂S₃ crystals in (100−x)GeS₂-xGa₂S₃ (x≤14.3) glasses corresponding to the experimental evidence of the phase transformation behavior. This scenario of intermediate-range structural order, firstly, includes the arrangement of structural units which is consistent with and provides an atomistic explanation of the compositional evolution of phase transformation behavior in these glasses.     

Crystallization and second harmonic generation in potassium-sodium niobiosilicate glasses

Transparent glasses having molar composition (23−x)K₂O·xNa₂O·27Nb₂O₅·50SiO₂ (x=0, 5, 10, 15 and 23) have been synthesized by the melt-quenching technique and their devitrification behaviour has been investigated by DTA and XRD. Depending on the composition, the glasses showed a glass transition temperature in the range 660-680 °C and devitrified in several steps. XRD measurements showed that the replacement of K₂O by Na₂O strongly affects the crystallization behaviour. Particularly, in the glasses with only potassium or low sodium content the first devitrification step is related to the crystallization of an unidentified phase, while in the glass containing only sodium, NaNbO₃ crystallizes. For an intermediate sodium content (x=10 and 15) a potassium sodium niobate crystalline phase, belonging to the tungsten-bronze family, is formed by bulk nucleation. This system looks promising to produce active nanostructured glasses as the tungsten-bronze type crystals have ferroelectric, electro-optical and non-linear optical properties. Preliminary measurements evidenced SHG activity in the crystallized glasses containing this phase.     

Processing and characterization of new passive and active oxysulfide glasses in the Ge-Ga-Sb-S-O system

New passive and active oxysulfide glasses have been prepared in the Ge-Ga-Sb-S-O system employing a two-step melting process which involves the processing of the chalcogenide glass (ChG) and its subsequent melting with amorphous GeO₂ or Sb₂O₃ powder. Optical characterization of the oxysulfide glasses has shown that the UV cut-off wavelength decreases with increasing oxygen content. Using Raman spectroscopy, correlations have been made between the formation of new Ge- and Sb-based oxysulfide structural units, the Sb content and the O/S ratio. We demonstrate the successful processing of active rare earth doped oxysulfide glasses by melting the chalcogenide glass with Er₂O₃ and Sb₂O₃ and also by melting the Er³⁺ doped chalcogenide glass with Sb₂O₃. Modification of the emission spectra at 1500 nm of Er³⁺ doped samples with the introduction of oxygen revealed that Er³⁺ most likely exists in dual O- and S-neighbor environments. Finally, the photo-response of these new glasses upon near-IR femtosecond laser irradiation has been investigated as a function of Sb content and O/S ratio and shows that the glasses are photo-sensitive to NIR fs laser light with the magnitude of the photo-sensitivity dependent on the glass’ Sb content and O/S ratio.     

Preparation of rare earth oxyfluorides and their properties as a material for fuel cell

The formation of rare earth oxyfluorides and their properties as an electrocatalyst and/or a solid electrolyte using for fuel cell were studied by means of x-ray and electrochemical methods.By a high temperature solid reaction between rare earth fluorides and rare earth or zirconium oxides not only the simple oxyfluoride such as NdOF, SmOF, CeOF and YOF but also the binary one written by Nd_1?xLn_xOF, (NdOF)_1?x(MO)_x and (ZrO₂)_1?x(LnF₃)_x were obtained, where Ln; Y, La, Nd, Sm and Yb, MO; alkaline earth oxide and Nb₂O₅. On the solid reaction process, it was found that the exchange reaction of anion, that is F? and O^2?, took place at first between the rare earth fluoride and the oxide. LnF₃ could form the solid solution with ZrO₂ at above 1200°C taking the fluorite structure in the composition range of below 30 mol%-LnF₃, so-called the stabilized zirconia.The crystal type of these oxyfluorides was any one of the rhombohedral, the cubic and the tetragonal. The cubic phase oxyfluorides contained Nd showed high electrocatalytic activity for both the hydrogen oxidation and the oxygen reduction. Then (NdOF.)_0.9(Nb₂O₅)_0.1 and (ZrO₂)_1?x(LnF₃)_x were found to act as the oxide ion conducting solid electrolyte.