Lead Fluoride Research Articles

Radiation study of Lead Fluoride crystals

Lead fluoride (PbF2) crystals represent an excellent and relatively innovative choice for high resolution electromagnetic calorimeters with high granularity and fast timing for high intensity environments. For this reason two PbF2 crystals, sized 5× 5 × 40 mm3, were irradiated with 60Co photons up to ∼ 4 Mrad and with 14 MeV neutrons up to a 1013 n/cm2 total fluence. Their loss in transmittance was evaluated at different steps of the photon and neutron irradiation campaign, resulting in a total of 30% loss above 350 nm. With crystals always kept in dark conditions, natural and thermal annealing, as well as optical bleaching with 400 nm light, were performed on the irradiated specimens, resulting in a partial recovery of their original optical characteristics.

Temperature-dependent potential for the molecular dynamics of the superionic conductor β-PbF2

Molecular dynamic (MD) calculations were performed to investigate the thermodynamic and structural properties of lead fluoride (PbF2) by using a proposed inter-ionic temperature-dependent potential. This potential allows calculating with high precision the linear thermal expansivity and the lattice parameter as a temperature function. In addition, the potential can be represented as a sum of two contributions, a temperature-independent potential added to another temperature-dependent potential, considered last as a correction justified by the one-dimensional Newtonian quantum equation. Two fitting regions were considered, the first region from 300 to 700 K and the other one from 700 to 900 K. These regions arise naturally due to the smooth and continuous transition that PbF2 undergoes until it reaches the superionic state and, allows us to model with high precision the anomaly in the dependence of the lattice parameter with the temperature of this material, a feature that until now under the molecular dynamic method has not been studied. These results are all in good agreement with the experimental measurements.

Organic phosphor and lead fluoride based luminescent hybrids

Powder hybrid materials based on the organic phosphor 8-hydroxyquinolate lithium and the inorganic matrix PbF2 have been synthesized. Powder hybrid materials were obtained by co-precipitation from aqueous-alcoholic solutions with ammonium fluoride under various conditions – different concentrations of the organic component, precursor solutions, the order of mixing the reagents: direct precipitation and reverse precipitation, providing a local excess of nitrate or fluorinating agent during the synthesis. Hybrid materials are single-phase powders, whose crystal structure corresponds to the rhombic phase of α-PbF2. All obtained hybrid materials showed effective broadband luminescence in the region of 390–700 nm. The shift of the photoluminescence bands to longer wavelengths relative to the initial Liq is observed, which is characteristic of lead luminescent complexes, which suggests the formation of new optical cents associated with Pbq2 or [PbqF]2, for all obtained hybrid materials. The formation of optical centers occurs as a result of an exchange reaction and the formation of new bonds between lead and organic ligands. Moreover, an increase in the concentration of the initial Pb(NO3)2 solution promotes a more complete course of the exchange reaction (up to 88%). During reverse deposition, a large fraction of Liq is captured by the crystallizing lead fluoride molecularly, and the completeness of the exchange reaction is generally lower than during direct deposition. The photoluminescence intensity during reverse deposition is 3 to 10 times higher than during direct deposition for different concentrations of reagents. The most intense luminescence is provided by the conditions of reverse precipitation with ammonium fluoride of a solution of lead nitrate with a concentration of 0.8 M and a Liq content of 1 wt.%.This research was funded by the Russian Science Foundation, Grant No. 19-79-10003.

Bis(imino)carbazolate lead(II) fluoride and related halides.

The versatility of a bulky bis(imino)carbazolate ligand in lead(ii) chemistry is illustrated by the synthesis of a soluble, heteroleptic lead(ii) fluoride and several halide (Cl, Br and I), amide and hydrocarbyl congeners. All complexes have been structurally authenticated, and a full set of 207Pb NMR data is discussed.

Evidence of selected nephrotoxic elements in Sri Lankan human autopsy bone samples of patients with CKDu and controls

BackgroundThis article describes the analysis and interpretation of data relating to the presence of cadmium, lead, mercury and fluoride in human bone samples obtained from cadavers of patients dying of Chronic Kidney Disease of uncertain aetiology (CKDu) in a case-control study, which the authors believe to be the first in Sri Lanka.MethodsThis is a case-control study comparing selected nephrotoxins levels in autopsy samples of bones from persons confirmed to have died of CKDu, and who had lived in a CKDu hotspot and controls with no history of abnormal kidney functions who had lived in areas having a low prevalence of CKDu.ResultsThe average age at death of the cases was 59.6 ± 15.1 (±SD), while that for controls was 58.0 ± 19.3 (±SD) years with no significant statistical difference. Calcium adjusted bone lead and bone fluoride levels were significantly higher among CKDu cases (n = 14) than those of controls (n = 33). Further, younger and older clusters of CKDu cases can be differentiated when the calcium adjusted lead content was considered. Younger patients reported higher lead content compared to the older group. Cadmium and mercury content did not show a remarkable difference among cases and controls.ConclusionsOur results show a significant accumulation of lead in bone tissue in persons who have died of CKDu which indicates a higher chronic exposure of the CKDu victims, to lead. Fluoride content in the bones of cases is also significantly high. The results indicate that a gradual reduction of glomerular filtration rate (GFR) may have occurred with the chronic exposure to lead. At a certain point of the threshold of low GFR, excretion of fluoride may be impaired, since the main excretory pathway of fluoride is via the kidneys. Fluoride accumulation in blood in turn may exacerbate nephrotoxicity, triggering a synergistic cascade of events which may lead to a further deterioration in the GFR. The extremely high fluoride content detected suggests a cumulative effect in people exposed to comparatively higher fluoride levels, most probably from drinking water.

A novel resonance method for determining the complex permittivity of local inclusions in a rectangular waveguide

A novel resonance method for determining the complex permittivity of materials in the X-band is proposed. A distinctive feature of this method is that the sample under test, located in a radio-transparent isotropic and homogeneous dielectric matrix, is both a local inclusion and the excitation element of the resonance in the microwave module ‘waveguide–dielectric matrix–inclusion’. The complex permittivity of an inclusion is determined by comparing the measured resonance frequency and quality factor with the computed database value. The permittivity and loss factor of microwave ceramics, natural granite and ferrite are investigated, as well as crystals of lead fluoride PbF2 doped with holmium trifluoride HoF3 and erbium fluoride ErF3 of different concentrations. The method allows the permittivity and loss tangent to be determined with uncertainties of 0.1% and 5%, respectively.

The impact of the lead on the physicochemical and optical properties of the fluorophosphate glasses doped by Nd3+ ions

Fluorophosphate glasses of the composition 5Ba (PO3) 2- (38-x) AlF3-57RF2-xNdF3 were obtained, where R = Ba, Ca, Sr, Mg, Pb; x = 0.5, 3, 5 mol%. It was found that the introduction of lead fluoride reduces the glass transition and crystallization temperatures. It has been shown that for all systems containing MgF2, the formation of a uovite phase is characteristic. The UV-cutoff has shifted from 200 nm to 250 nm.

Reactivity of the anion acceptor in electrolyte: An important factor in achieving high electrochemical performance of a lead (II) fluoride electrode in a fluoride shuttle battery

The electrochemical reaction in a fluoride shuttle battery (FSB) requires an organic solvent containing a supporting electrolyte salt. To dissolve an insoluble inorganic fluoride compound (e.g., cesium fluoride (CsF)) in an organic solvent (e.g., bis[2-(2-methoxyethoxy)ethyl]ether [tetraglyme, G4]), an anion acceptor (AA) (e.g., triphenylborane (TPhB) or triphenylboroxine (TPhBX)) is typically added. This study investigates the effect of AA type and CsF/AA molar ratio on the electrochemical performance of a lead (II) fluoride (PbF2) FSB electrode. The PbF2 electrodes were cycled in an FSB with G4 containing CsF (0.45 mol dm−3) and TPhB (0.5 mol dm−3) as the electrolyte. The capacity was high during the first cycle, but drastically decreased during subsequent cycling. X-ray diffraction (XRD) and atomic absorption spectrometry (AAS) revealed Pb formation during the discharging process, but PbF2 formation and Pb dissolution during the charging process. The loss of active material through Pb dissolution caused the capacity degradation. Changing the AA type from TPhB to TPhBX promoted Pb dissolution, thereby aggravating the capacity retention problem. In contrast, increasing the CsF concentration from 0.45 mol dm−3 to its saturation concentration effectively preserved the capacity during cycling by suppressing the Pb dissolution, as confirmed in the AAS results. However, increasing the CsF concentration deteriorated the discharge and charge capacities of the PbF2 electrode. Changing the AA type from TPhB to TPhBX in the electrolyte containing saturated CsF increased the discharge and charge capacities during the first cycle, and maintained a high capacity in the subsequent discharging and charging processes, as supported in the XRD results. Overall, the AA type and CsF concentration in the electrolyte strongly affected the electrochemical performance of the PbF2 electrodes. Thus, an FSB with high electrochemical performance requires judicious selection of both AA type and CsF/AA ratio.

Simulation study to improve the performance of a whole-body PbF2 Cherenkov TOF-PET scanner

Using Cherenkov radiation in positron emission tomography (PET) has the potential to improve the time of flight (TOF) resolution and reduce the cost of detectors. In previous studies promising TOF results were achieved when lead fluoride (PbF2) crystals were used instead of a scintillator. In this work, a whole-body PbF2 Cherenkov TOF-PET scanner was simulated and optimized. Different configurations of the PbF2 crystals and their surface treatment were considered. Also evaluated was the influence of the crystal-photodetector coupling and of the detection efficiency of the photodetectors. Of special interest is a whole-body PbF2 Cherenkov TOF-PET scanner with a multi-layer detector, which improves the time resolution and reduces the parallax error, without compromising the detection efficiency. Images of a phantom were reconstructed for different configurations of the simulated whole-body PbF2 Cherenkov TOF-PET scanner and the quality of images was compared to that of a whole-body TOF-PET scanner with standard LSO scintillators. The TOF resolution of the whole-body PbF2 Cherenkov TOF-PET scanner with a multi-layer detector was 143 ps FWHM, out of which the fundamental limitation due to light production and transportation was only 22 ps FWHM.

Influence of Lead Fluoride Substitution on the Physical Properties of ($$ {\text{Cu}}_{0.5} {\text{Tl}}_{0.5} $$)-1223 Phase

This work reveals the influence of lead fluoride on the physical properties of high-temperature superconductor samples \( \left( {{\text{Cu}}_{0.5 - x} {\text{Tl}}_{0.5} {\text{Pb}}_{x} } \right){\text{Ba}}_{2} {\text{Ca}}_{2} {\text{Cu}}_{3} {\text{O}}_{10 - \delta - y} {\text{F}}_{y} \), with (0.00 ≤ x ≤ 0.10). The samples under investigation were synthesized by solid-state reaction method at normal pressure. Ion beam analysis techniques were employed to determine the elemental content of the starting materials. The fluorine content “y” was estimated using the proton-induced gamma-ray emission technique by the aid of a 3 MeV proton beam. It was correlated to the oxygen content which was obtained using the Rutherford backscattering technique. Moreover, the samples were characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and Fourier transform infrared (FTIR). The XRD data have indicated that the partial replacement of \( {\text{Cu}}^{2 + } \) ions by Pb2+ ions and oxygen by fluorine in the reservoir layer do not alter the tetragonal structure of the samples. On the other hand, the values of the lattice parameters a and c were found to be varied with x according to the difference in the ionic radii of \( {\text{Pb}}^{2 + } \;{\text{and}}\;{\text{Cu}}^{2 + } \) as well as to the oxygen content. SEM analysis has revealed that lead fluoride substitutions improve the inter-grains connectivity of the prepared samples. FTIR analysis has shown that the apical oxygen, planar and the oxygen in reservoirs layers, modes are observed around 415–524 cm−1, 564–579 cm−1 and 680 cm−1, respectively. Moreover, a shift in all absorption peaks was observed in the pure sample of (CuTl-1223) phase, and new peaks were appeared according to the values of x. The physical properties of the samples were investigated using electrical resistivity and ac magnetic susceptibility measurements at different values of the applied ac magnetic field. The granular response shows both inter-granular and intra-granular contributions. The values of the superconducting transition temperature (\( T_{\text{c}} \)) have shown an increase with x up to 0.06 wt% followed by a decrease with further increase in elements substitution.

The effect of the addition of CaF2 and PbF2 on boro-tellurite glasses doped with chromium ions

This article presents the impact of CaF2 and PbF2 on boro-tellurite glasses, together with preparation of glass, primary experimental techniques, modern technology and progress, particularly the development of transition metal ion doped boro-tellurite glasses for optical glass related applications. Physical and structural investigations on chromium doped boro-tellurite glasses have been studied as a function of metal fluorides. Several physical and optical parameters have been obtained and their results are explained clearly. High density and refractive index values were observed for lead fluoride doped boro-tellurite glasses which are the essential properties of the materials for applications in fiber optical communication. Electron Paramagnetic Resonance (EPR) spectrum have shown two resonance signals at low and high field regions. FTIR spectra revealed that the B–O–B vibrations are due to various BO3 and BO4 units and Te–O vibrations are from different TeO3 and TeO4 units. Deconvoluted Raman spectra being used to locate the band positions in the spectra. Raman spectra confirmed that the presence of stretching vibrations of Te–O–B links, B–O links in BO4 units. The conversion of Te–O linkages to Te–F linkages by the addition of metal fluorides is observed from of Raman spectra.

Equations of State of Simple Solids (Including Pb, NaCl and LiF) Compressed in Helium or Neon in the Mbar Range

The equations of state measured under ambient temperature in the Mbar range are reviewed, focusing on experiments using diamond anvils cells with a quasi-hydrostatic pressure transmitting medium (helium or neon) and coupled with X-ray diffraction. Equations of state (EoS) parameters are listed with an unified pressure metrology for all data. This metrology is based on the efforts made in the 2000s to update the ruby luminescence pressure scale, after the collection of original data. To complete this database, unpublished P-V data for lead (Pb), sodium chloride (NaCl) and lithium fluoride (LiF) are also provided with the same metrology. Systematic effects of the pressure metrology on the EoS parameters are discussed.

Binary Lead Fluoride Pb3 F8.

The binary lead fluoride Pb3F8 was synthesized by the reaction of anhydrous HF with Pb3O4 or by the reaction of BrF3 with PbF2. The compound was characterized by single‐crystal and powder X‐ray diffraction, IR, Raman, and solid‐state MAS 19F NMR spectroscopy, as well as thermogravimetric analysis, XP and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy. Solid‐state quantum‐chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound.

Influence of lead fluoride on the mechanical properties of ($$\text{Cu}_{0.5} \text{Tl}_{0.5}$$): 1223 Phase

Influence of lead fluoride on the mechanical properties of ($$\text{Cu}_{0.5} \text{Tl}_{0.5}$$): 1223 Phase

Spectroscopic and lasing properties of Er3+/Yb3+-doped fluorophosphate glass with small additives of phosphates

The influence of lead fluoride on the formation and luminescent properties of glass and glass-ceramics has been studied. Using the Judd-Ofelt theory, the intensity parameters Ωt have been obtained. The stimulated emission cross-section of the 4I13/2→4I15/2 transition has been determined. The energy transfer from ytterbium to erbium with 96% efficiency was found with an erbium laser level lifetime of ∼8 ms. The gain shape of the glass under study has been found to be smoother than for phosphate glasses, which makes the former very attractive gain material for ultra-short laser sources. For the first time, fluorophosphate glass-ceramics were obtained with nanocrystals doped with erbium and ytterbium ions.

Efficiency of a Cherenkov based PET module with an array of SiPMs

The detectors in positron emission tomography (PET) can be based on detection of Cherenkov light instead of the traditional approach of using scintillation light. This enables excellent time resolution that can be used in time-of-flight (TOF) PET, but it proved difficult to achieve efficiency in detection of annihilation gammas comparable to traditional methods. The Cherenkov method however has another advantage — low cost of the most suitable conversion material (lead fluoride) compared to the most commonly used scintillators. Especially when incorporating silicon photomultiplier (SiPM) photodetectors, such PET detectors could be realized at a very competitive price. In this work the performance of such PET module is presented, with an emphasis on the efficiency of detection. A module consisting of 4 × 4 lead fluoride Cherenkov radiator array coupled to a Hamamatsu 4 × 4 SiPM array was assembled and its performance was tested using annihilation gammas from a sodium source.

Structural evolution of luminescence nanoparticles with rare-earth ions in the oxyfluoride glass ceramics

The structure of up-conversion luminescent nanoparticles in oxyfluoride glass ceramics doped with rare-earth ions has been studied by using small-angle neutron scattering and atomic force microscopy. The formation of rather large amorphous nanoparticles with an average size of about 30 nm was found for the initial system. At temperature treatment above 380°С with increased processing time, the initial large nanoparticles divide into the smaller ones with the average sizes in the range of 14–20 nm. It is assumed that this process corresponds to crystallization of the lead fluoride component with the formation of up-conversion luminescence centers. The structural parameters, morphology and size distributions of both amorphous and crystalline nanoparticles have been obtained.

Molecular dynamics simulation of ionic transport and thermodynamic properties in β-PbF2

In this work, a study through the use of molecular dynamics of the ionic conduction processes in lead fluoride in its beta phase, as well as the variation of the specific heat capacity with the temperature increase at constant pressure, is presented. In order to carry out the molecular dynamic simulations, the classic simulation package DL_POLY and the well-known interatomic interaction potentials of Walker et al. were used. This research shows how the calculated ionic conductivity is in agreement with different reported experimental measurements in the non-superionic region; however, this finding presents discrepancies for the superionic region. The molecular dynamics calculations for the specific heat cp in this material show high coincidence in the non-superionic region (300–600 K). Simulations by molecular dynamics show that fluorine ions behave as a liquid flowing through the structure of fixed ions of lead.

Charge and Discharge Reactions of a Lead Fluoride Electrode in a Liquid‐Based Electrolyte for Fluoride Shuttle Batteries:‐The Role of Triphenylborane as an Anion Acceptor‐

AbstractLead fluoride (PbF2) is a promising electrode material for fluoride shuttle batteries (FSBs) owing to its high theoretical capacity (219 mAh g–1). In this study, the discharge and charge capacities of a PbF2 electrode were measured using a bis[2‐(2‐methoxyethoxy)ethyl] ether containing cesium fluoride and triphenylborane as an electrolyte. A high specific capacity was maintained during both the discharge and charge processes in the first cycle, but the capacity decreased from the first charge process to the following discharge process. To clarify the electrochemical reaction mechanism, the dissolution and change in the electronic state of Pb at the PbF2 electrode during the discharge and charge processes were evaluated via atomic absorption spectrometry (AAS) and X‐ray photoelectron spectroscopy (XPS). The results obtained from AAS and XPS indicated that Pb was formed during the discharge process. Conversely, the formation of PbF2 and dissolution of Pb coexisted within the wide range of charge process. The PbF2 could react in the following cycle, but the dissolved Pb was unable to contribute to the following discharge/charge reaction. Therefore, after the initial charge process, the capacity decreased.

Lead fluoride Cherenkov detector read out by avalanche photodiodes for measuring the intensities of pulsed antiproton beams

A Cherenkov detector based on an array of five lead fluoride ($\beta$-PbF$_2$) crystals of size 30 mm$\times$30 mm$\times$160 mm read out by reverse-type avalanche photodiodes (APD's) of active area 10 mm$\times$10 mm was used to measure the flux of secondary particles emerging from the annihilation of pulsed beams of antiprotons at the Antiproton Decelerator of CERN. We compared the relative photon yields of radiators made of $\beta$-PbF$_2$, fused silica, UV-transparent acrylic, lead glass, and a lead-free, high-refractive-index glass. Some {\it p-i-n} photodiodes were also used for the readout, but the output signals were dominated by the nuclear counter effect (NCE) of secondary particles traversing the 300 $\mu{\rm m}$ thick depletion regions of the photodiodes. Smaller NCE were observed with the APD's, as the maximum electronic gain in them occurred predominately for electron-ion pairs that were generated in the thin ${\it p}$-type semiconductor layer that proceeded the {\it p-n} junction of high electric field where amplification took place.