PbO PbF2 Research Articles

PbF2 as a key modulator of gamma radiation shielding in PbO–PbF2–B2O3–SiO2 glass systems

PbF2 as a key modulator of gamma radiation shielding in PbO–PbF2–B2O3–SiO2 glass systems

PbO–PbF2–B2O3–SiO2 Glasses: Exploring the Impact of PbF2 in Modulating Radiation Shielding Characteristics

PbO–PbF2–B2O3–SiO2 Glasses: Exploring the Impact of PbF2 in Modulating Radiation Shielding Characteristics

A Study of PbF2 Nanoparticles Crystallization Mechanism in Mixed Oxyde-Fluoride Glasses

Samples of nanocrystalline PbF2 glass ceramics were obtained by heat-treating SiO2–GeO2–PbO–PbF2–CdF2 glasses. The Ho2O3 and Tm2O3 doping effects on the structural features of PbF2 nanoparticles were studied using small-angle X-ray scattering and X-ray diffraction methods. The enlargements of the average sizes of nanoparticles and the sizes of local areas of density fluctuations have been found to be correlated with an increase in concentrations of Ho2O3 and Tm2O3 in initial glasses. A variation in the concentrations of Ho2O3 and Tm2O3 does not affect the morphology and fractal dimension of the formed PbF2 nanoparticles.

Synthesis, structure and properties of PbO–PbF2–B2O3–SiO2 glasses

The structure, thermal and some physical properties of lead fluoroborate glasses containing 30 mol% SiO2 have been investigated by differential thermal analysis, X-ray diffraction and Fourier-transform infrared spectroscopy. The glasses were prepared by the conventional melt-quenching method. Fourier-transform infrared spectroscopy results showed that the network of these glasses consists mainly of BO3, BO4, SiO4, and PbO4 structural units. The thermal stability of the glass samples determined by differential thermal analysis was found to be about 80°C. Dilatometric measurements showed that the glass transition temperature and dilatometric softening temperature decrease with increasing lead content, whereas the coefficient of thermal expansion increases. The density and molar volume increased with the increase in lead content. The conductivity of the investigated glasses mainly depends on the mobility of F– and Pb2+ ions. The variation in volume resistance upon changing the composition has been correlated with the structural changes in the glass network. The results obtained in this study indicate that the investigated glasses can be potential candidates for advanced technologies as solder and sealing materials.

Yb3+/Er3+−codoped GeO2–PbO–PbF2 glass ceramics for ratiometric upconversion temperature sensing based on thermally and non-thermally coupled levels

The contactless real-time temperature sensing technique with high temporal and spatial resolution is in high demand for the countless applications. Here, the Yb3+/Er3+−codoped GeO2–PbO–PbF2 glass ceramics synthesized via the melt-quenching technique has been presented as an optical thermometer. The thermal sensing was designed based on the temperature dependent fluorescence intensity ratios of thermally (2H11/2 and 4S3/2) and non-thermally (2H11/2 and 4F9/2) coupled Er3+ levels. The ratiometric techniques provide the thermal sensing within the temperature range of 300–466 K. The absolute and relative thermal sensitivities as well as the temperature resolution were calculated and compared with other Yb3+/Er3+-doped materials. The temperature of the microelectronic component on the printed circuit board was defined using the optical thermometry as a proof of concept revealing Yb3+/Er3+−codoped GeO2–PbO–PbF2 phosphor to be a promising candidate for precise non-contact thermal sensor.

Optical temperature sensing in Tm3+/Yb3+-doped GeO2–PbO–PbF2 glass ceramics based on ratiometric and spectral line position approaches

Development of new contactless thermometers with improved characteristics is highly demanded for science and technology. In this work, we present upconverting Tm3+/Yb3+-doped GeO2–PbO–PbF2 glass ceramics as optical temperature sensor. Upon 973 nm laser excitation, sample generates intense emission bands from blue to NIR regions due to ladder-like energy levels of Tm3+ ion. A ratiometric technique involving the Tm3+ thermally and non-thermally coupled levels (1G4(a), 1G4(b), 3F2,3, 3H4) and spectral line position of 3H4–3H6 transition was used to provide thermal sensing in the 300–466 K temperature range. The performance of suggested sensing parameters was compared and discussed in terms of relative thermal sensitivity. The maximal thermal resolution, which can be achieved using Tm3+/Yb3+-doped GeO2–PbO–PbF2 thermometers, is better than 1 K at both 303 and 465 K. The obtained results show the potential use of GeO2–PbO–PbF2: Tm3+,Yb3+ phosphor for optical sub-degree temperature sensing.

The role of the REE ions in the glass systems TeO2–PbO·P2O5–PbF2:MF3 (M–Er, Nd)

The glasses doped with the Er3+, Nd3+ ions were synthesized in the oxyfluoride system TeO2–PbO·P2O5–PbF2:МF3 and studied by the IR and Raman spectroscopy (including low-frequency range of spectra), DSC, SAXS and luminescence methods. The role of REE ions in the structure forming, crystallization and luminescent properties of glasses is identified. It was found that the rare-earth element ions enter into the medium range order of glass structure and act as crystallite forming nuclei. The contribution of the Er3+ photoluminescence with emission levels at 524, 530, 545, and 554 nm into the inelastic scattering spectrum of glasses in the system of TeO2–Pb2O5·PbO–PbF2:xErF3 has been revealed.

Mechanisms of Up-Conversion Luminescence in Glass-Ceramics Containing Er:PbF2 Nanocrystals

Transparent oxyfluoride germanosilicate glass-ceramics containing Er:PbF2 nanocrystals is synthesized on the basis of SiO2–GeO2–PbO–PbF2 initial glass doped with Er2O3. The glass-ceramics is characterized by yellow-green luminescence, the intensity of which is ~12-times higher than that for the initial glass. The redistribution of the intensity between green and red emission bands after the glass heat-treatment is explained using data of the lifetime measurements for six excited states of Er3+ ions from 4 I 11/2 to 2 H 11/2. A substantial increase of the lifetime of the 4 F 9/2 state (from 0.6 to 71 μs) is detected for the glass-ceramics as compared to the initial glass. UV up-conversion luminescence is observed for the glass-ceramics. The mechanisms of the up-conversion for 11 emission lines in the UV, blue, red, and deep-red spectral regions are discussed.

Up-Conversion Luminescence in Oxyfluoride Glass-Ceramics with PbF2:(Yb3+, Eu3+, RE3+) (RE = Tm, Ho, OR Er) Nanocrystals

Transparent oxyfluoride glass-ceramics containing PbF2:(Yb3+, Eu3+, RE3+) (RE = Tm, Ho, Er) nanocrystals were synthesized by secondary thermal treatment of low-melting SiO2–PbO–PbF2–CdF2 glasses. The optical absorption and luminescence of the rare earth ions were investigated. Multi-color (orange, yellow, green, and blue) upconversion luminescence was detected with excitation at 960 nm by an InGaAs laser diode. The luminescence color characteristics could be controlled by varying the heat treatment regime.

Spectral and Luminescent Properties of Oxyfluoride Glasses Codoped with (Yb3+, Eu3+) and (Yb3+, Tb3+)

The spectral and luminescent properties of SiO2–PbO–PbF2–CdF2 oxyfl uoride glasses doped with Yb3+, Eu3+, and Tb3+ were investigated. The lifetime τ( 5D0) of Eu3+ in glasses doped with Eu2O3 was 1.73 ms; τ( 5D4) of Tb3+, 2.25 ms. Intense red and green up-conversion luminescence due to cooperative energy transfer from Yb3+—Yb3+ pairs to Eu3+ and Tb3+ was observed for glasses codoped with (Yb3+, Eu3+) and (Yb3+, Tb3+) upon excitation at 960 nm into the Yb3+ absorption band. Down-conversion luminescence of Yb3+ ions in the vicinity of ~1 μm was detected upon excitation by UV light of wavelength 355 nm.

Luminescence of Oxyfluoride Glasses Containing Yb3+–RE3+ Ions

The optical absorption and up-conversion luminescence of oxyfluoride glasses in the system SiO2–PbO–PbF2–CdF2 coactivated by Yb3+–RE3+ ions (where RE = Er, Tm, Ho, Dy, Pr, or Tb) are investigated. Excitation with a laser diode in the IR range (960 nm) gives intense green, blue, and red luminescence. The color characteristics of the up-conversion luminescence in the CIE 1931 system are determined. The efficiency of energy transfer from the Yb3+ to the RE3+ ions is found to be 70% for RE = Er, Tm, and Ho. The efficiency of cooperative energy transfer reaches 10% for glass with Yb–Tb ions.

Yellow Up-Conversion Luminescence of Transparent Glass Ceramics with Erbium Ions

A transparent glass ceramic, containing lead fluoride β-PbF2 nanocrystals with erbium ions Er3+ (average diameter 8.5 nm), was synthesized by means of secondary thermal treatment of the initial oxyfluoride glass of the system SiO2–GeO2–PbO–PbF2, doped with Er2O3. Its thermal and structural properties, optical absorption, and up-conversion luminescence were studied. The glass ceramic obtained holds promise as a luminophore and makes it possible to obtain intense yellow luminescence by excitation in the IR range of the spectrum.

Influence of sesquioxides on luminescence features of Nd3+ ions in PbO–PbF2–B2O3 glass system

The emission characteristics of Nd3+ ions in PbO–PbF2–B2O3–M2O3 (M=Y, Sc, Al) glasses were studied as a function of M2O3 concentration. The IR spectral investigations have indicated that the network of the glass mixed with Y2O3 is more depolymerized when compared with other two sesquioxides. The optical absorption, luminescence spectra and fluorescence decay curves of these glasses were studied as functions of concentration of M2O3. The luminescence spectra of these glasses have exhibited three NIR bands corresponding to the transitions 4F3/2→4I9/2, 4F3/2→4I11/2 (at 1.06μm) and 4F3/2→4I13/2. A clear enhancement in the luminescence emission corresponding to these transitions has been observed with increase in the concentration of M2O3 upto 8.0mol%. The comparison of emissive characteristics of the glasses mixed with three sesquioxides indicated the highest luminescence efficiency for Y2O3 mixed glasses among the three series glasses studied. The increase of luminescence efficiency has been attributed to the possible declusterization of Nd3+ ions by M3+ ions in the glass network. The reasons for low luminescence quenching observed in case of Y2O3 mixed glasses have been explored in terms of the ionic radii of the sesqui-ions and their possible positions in the glass network.

Cooperative up-conversion in Eu3 +,Yb3 +-doped SiO2–PbO–PbF2–CdF2 oxyfluoride glass

Novel oxyfluoride glass doped with YbF3 and Eu2O3 is synthesized in the SiO2–PbO–PbF2–CdF2 system by melt-quenching technique. Its physical properties, as well as the optical absorption of Eu3+ and Yb3+ ions are studied. Spectroscopic properties of Eu3+ ions are modeled within modified Judd–Ofelt theory, yielding absorption oscillator strength, luminescence branching ratios and radiative lifetime of 5D0 state. Intrinsic emission of Eu3+ ions under direct excitation in the UV, as well as up-conversion luminescence under near-IR excitation via cooperative energy transfer, 2Yb3+→Eu3+, are studied. In the latter case, the glass provides intense reddish-orange emission with CIE coordinates x=0.636, y=0.363. The asymmetry parameter R for Eu3+ emission in the studied glass is about 8. The efficiency of this transfer mechanism is estimated from shortening of 2F5/2(Yb3+) lifetime to be 10±1%.

New Luminescing Oxyfluoride Glass with Europium and Ytterbium Ions

New oxyfluoride glasses containing Eu3+ and Yb3+have been synthesized in the system SiO2–PbO–PbF2–CdF2 and their physical-chemical properties and the optical absorption and up-conversion of luminescence have been studied. Intense orange-red luminescence (color coordinates x = 0.64, y = 0.36) peaking near 612 nm was obtained by excitation in the IR range by a commercially available laser diode. This glass is promising for obtaining nano-phase luminescing glass-ceramics for use in up-conversion luminophores and solid-state lasers.

White light generation from Dy3+ doped tellurite glass

This paper reports on the spectral results of Dy3+ (1.0mol%) ions-doped TeO2–ZnO–PbO–PbF2–Na2O (TZPPN) glass. Raman spectrum measurements, differential thermal analysis (DTA) profiles of this rare-earth ion-doped glass were carried out. From the DTA thermogram, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures were evaluated. Direct and indirect optical band gaps were calculated based on the glasses UV absorption spectra. From the absorption spectra, Judd–Ofelt (J–O) intensity parameters, Ωk, were calculated. Using J–O intensity parameters, several radiative properties such as spontaneous transition probabilities (AR), radiative branching ratios (βR) and radiative lifetimes (τR) were determined for the excitation level 4F9/2. From the emission spectra, a strong yellow emission at 574nm (4F9/2→6H13/2) was observed and it also showed a combination of blue and red emission bands for this glass. The stimulated emission cross-section σ(λp) was also evaluated for the 4F9/2→6HJ (J=11/2, 13/2, and 15/2) transitions. This study indicates that 1mol% Dy2O3-doped tellurite glass can be considered for white light generation with the excitation of blue light (454nm).

Influence of sesquioxides on fluorescence emission of Yb3 + ions in PbO–PbF2–B2O3 glass system

Yb3+ ions doped lead oxyfluoro borate glasses mixed with varying concentrations of three interesting sesquioxides (viz., M2O3=Al2O3, Sc2O3, Y2O3) were synthesized. The emission spectra of each series of glasses were recorded and characterized as a function of concentration of sesquioxides. The luminescence spectra of the three series of glasses excited at 970nm have exhibited intense band in the NIR region corresponding to 2F5/2→2F7/2 transition. The emission spectra of all the three series of glasses found to be partially overlapped with the absorption band. The comparison of Stokes shift indicated the highest value for Y2O3 mixed glasses. From these spectra, the absorption and emission cross-sections and also life time of 2F5/2 level of Yb3+ ions have been evaluated. The luminescence cross section is found to be the highest for Y2O3 mixed glasses among the three series of the glasses studied. The reasons for such variations have been discussed in the light of varying degree of structural modifications at the vicinity of Yb3+ ions in the glass network with the support of IR spectral results of these glasses.

Concentration effect of Sm3+ ions in B2O3–PbO–PbF2–Bi2O3–ZnO glasses – Structural and luminescence investigations

Concentration dependent spectroscopic properties of Sm3+ ions are investigated in the prepared xSm:PbFB lead fluorobororate glasses with the composition (40−x)B2O3+20PbO+16PbF2+12Bi2O3+12ZnO+xSm2O3 (where x=0.05, 0.1, 0.5, 1, 2 and 3wt.%). Surface morphological analysis and structural behaviors of the prepared glasses have been explored through SEM, EDX, XRD, FTIR and Raman spectral analysis. The amorphous nature of the prepared glasses have been confirmed through XRD spectral analysis. The presence of BO3, BO4, B–O–B and Pb/Bi–O–B vibrational stretching units in the prepared glasses are confirmed through FTIR and Raman spectral analysis. The optical characterizations were carried out using UV–vis–NIR absorption, luminescence spectra and decay curves of the present glasses. The calculated bonding parameter (β¯ and δ) values reveal the ionic nature of the Sm–O bond in the prepared glasses. The Judd–Ofelt intensity parameters, Ωλ, were evaluated from the measured oscillator strength of the various absorption bands to study the bonding environment around the Sm3+ ions in the prepared glasses. From the JO intensity parameters and emission spectral measurements, the radiative properties such as stimulated emission cross-section (σPE), branching ratio (βR) and radiative lifetime (τR) for the 6HJ=5,7,9,11 emission transitions have been calculated. The experimental lifetime for the excited 4G5/2 level of the Sm3+ ions in the prepared glasses were calculated from the decay analysis and it is found to decrease with the increase in Sm3+ ion content. The decay curves are found to be non-exponential for the higher concentration of Sm3+ ion which is due to the efficient energy transfer between Sm3+–Sm3+ ions. To understand the nature of the energy transfer, the non-exponential decay rates were fitted to Inokuti–Hirayama (IH) model for S=6 which reveals that the energy transfer process is of dipole–dipole in nature. Among the prepared glasses, 0.5SmPbFB glass exhibit higher values of emission characteristic parameters and quantum efficiency for the 4G5/2 level suggesting that 0.5SmPbFB glass could be useful for optoelectronic device fabrication and laser applications.

Domain, dielectric and optical studies in antiferroelectric (Pb, La) (Zr, Sn, Ti)O3 single crystals

Antiferroelectric (Pb, La) (Zr, Sn, Ti)O3 (PLZST) single crystals have been successfully grown by flux method using PbO–PbF2–B2O3 as the flux. The obtained crystals are pale yellow in color and translucent. Domain structures, dielectric constants and optical transmission measurements have been performed on the 〈001〉-oriented PLZST single crystals. Two types of domains, namely, 90° and 180° domains, are observed. The extinction of 90° domains at P/A: 0° reveals a tetragonal structure in the crystal. The sequence of phase transitions from antiferroelectric to ferroelectric and then paraelectric has been established with increasing temperature. According to the modified Curie–Weiss relationship, the PLZST crystal is in an intermediate state between normal and relaxor antiferroelectrics. The broad optical transparent region (from 0.4 to 7.0μm) and high optical transmittance (up to 65%) indicate that PLZST crystals are promising for optical uses.

Growth and characterization of Pb0.97La0.02(Zr0.66Sn0.27Ti0.07)O3 antiferroelectric single crystals

Single crystals of Pb0.97La0.02(Zr0.66Sn0.27Ti0.07)O3 (PLZST) with the composition near the morphotropic phase boundary were grown by the flux method. The PbO–PbF2–B2O3 system was used as a solvent. PLZST single crystals with the size of 4–6 mm are obtained and these crystals are slightly translucent after polishing. The splitting of (200) reflection peak indicates that the obtained crystals are of a single phase with tetragonal perovskite structure. The element contents of the grown crystals were measured by inductively coupled plasma atomic emission spectrometry. The chemical composition of the crystals is Pb0.979La0.014(Zr0.666Sn0.285Ti0.049)O3. Thermal properties and dielectric properties of PLZST single crystals were studied. The results show that flux-grown PLZST single crystals exhibit obvious endothermic processes and relaxor behaviors near the phase transition temperatures.