Lead Iron Phosphate Research Articles

Micro‐hardness and gamma‐ray attenuation properties of lead iron phosphate glasses

For safe immobilization of nuclear waste, lead-iron phosphate glasses are promising as high-level commercial and defense materials. In this research article, the compositional, elastic, and gamma shielding properties of the glasses containing (80 − x)P2O5– xFe2O3–20PbO with x = 20, 25, 30, 35 mol% were reported. The compositional and elastic parameters including the micro-hardness of the investigated glass samples were obtained based on Makishima-Mackenzie’s theory (MM-theory) and R model. We found that the deviation between these two methods decreased as Fe2O3 concentrations increased from 20 to 35 mol %. Additionally, γ-ray attenuation properties of the P2O5– Fe2O3–PbO glass system were evaluated using Geant4 simulation toolkit. The simulation results were compared with the theoretical ones extracted from Py-MLBUF software. The obtained results reveal that the MACs of the glasses vary from 0.030 to 40.014 cm2/g for PFP-A, from 0.031 to 41.502 cm2/g for PFP-B, 0.031 to 43 cm2/g for PFP-C and from 0.031 to 44.400 cm2/g for PFP-D. Maximum Zeff values of present glasses are obtained at 0.10 MeV whereas minimum Zeff values are obtained at 1.5 MeV. Finally, the fundamental γ-ray attenuation properties of the P2O5– Fe2O3–PbO glass system are found to be comparable with those of traditional and commercial radiation shields such as RS-253-G18 and RS-360 commercial glasses, ordinary concrete, barite concrete and TBZP10 from scientific literature. The results indicated that MFPs of the investigated glasses are lower than those of RS-360 glass, but they are higher than those of barite concrete and TBZP10.

Development of advanced, transparent radiation shielding glass possessing phosphate and lead ions in the glassy matrix

Glasses of the system (90-x) P2O5–x PbO–10Fe2O3 (where 25 ≤ x ≤ 45) mol % were prepared by utilizing meltdown quenching technique. Optical and FTIR spectroscopic measurements are utilized to investigate and characterize the given compositions of lead–iron phosphate glasses. During this work, it is aimed to check the chance of utilizing the prepared glass as a good shielding material for radiation. So as to estimate gamma-ray shielding properties of glass samples, mass attenuation coefficients have calculated with the XCOM computer program. The values of half-value layers are calculated. The changes within FTIR spectra because of the presence of metal oxides were referred to the various housing positions and physical properties of various Fe2+ and Pb2+ ions. Calculations of optical band gap energies from the ultraviolet light information were given to examine the chance of utilizing these glasses as gamma radiation shielding material. The results of each optical and FTIR spectra of the studied glasses showed that the dual role of Pb2+ and Fe 3+ ions as glass modifier and former, therefore, the glass is denser and a lot of compacts, therefore reducing its molar volume and increasing its hardness, that confirms their shielding behavior and suitability as the radiation shielding candidate materials.

Glass waste form options for rare-earth fission products from electrochemical reprocessing

This paper describes a first-of-a-kind study where lead tellurite (Pb-Te-O), iron phosphate (Fe-P-O), and lanthanide aluminoborosilicate (LABS) glass waste forms were evaluated for treating and/or immobilizing waste streams containing high rare-earth (RE) content in different forms, e.g., RECl3, REOCl, and/or REOx. Results from this study show that NdOCl can be immobilized in 78TeO2-22PbO glass at up to 10 mass%. Higher loadings of up to 15 mass% were demonstrated, but with a small fraction of crystallization. Two Fe-P-O glasses produced from either RECl3 (RE = Nd,Ce) or NdOCl revealed products with very similar properties, demonstrating that the phosphate process can be used to dechlorinate a variety of RE-containing halide-based waste streams. The LABS glasses produced from Nd2O3 or NdOCl showed similar properties, but the LABS-NdOCl glass did have some residual Cl present. Characterization is provided for all waste forms including chemical analysis, X-ray diffraction, and bulk density.

Preparation and Study of Corrosion Behavior of Some Simulated Radioactive Waste Glasses

To safe environment from radioactive waste it is important to fix them as radioactive waste glasses. The corrosion behavior of radioactive waste glasses in water is significantly important. Radionuclides return to the biosphere by means of leaching from waste form into ground water. Finally the ground water containing the radionuclide are transported to the surface. In this study, the preparation, characterization and leaching behavior of some borosilicate (BS) and lead iron phosphate (LIP) of different chemical composition doped with simulated nuclear waste oxide were investigated. We measured the pH found to be in the range from 6.78 up to 7.79 of the leachate solution at normal temperature and at varying time intervals. Leaching study of these glasses were conducted with the help of Soxhlet distillation apparatus with distilled water upto 24 hours and for BS9 - BS12 upto 100 hours duration. Weight losses were are measured with respect to time of leaching. Leach rate of some borosilicate glass samples loaded with uranium are calculated from surface area measurements. The results are reported in the range 1.34x10-4 g.m-2.hr-1 and 6.26 x 10-4 g.m-2.hr-1 respectively at 90°C.

Effects of heat treatment on the structural and electrical conductivity of Fe2O3–P2O5–PbO glasses

Glasses having compositions xFe2O3–(80 − x)P2O5–20PbO with x = 20, 25, 30, 35 mol% were prepared by traditional glass melt-quenching method. The effects of the heat treatment of glasses on their structural and electrical conductivity were studied by X-ray diffraction (XRD), differential scanning calorimeter, density (ρ) and dc conductivity (σ). The glass transition temperature (Tg) was observed to increase with Fe2O3 content. The density of the prepared glass and corresponding glass–ceramics increases with Fe2O3 content. XRD of as-quenched glass samples confirm the amorphous nature. Triclinic lead iron phosphate PbFe2(P2O7)2 is the main crystalline ceramic phase formed after heat treatment at 973 K, of 20 and 25 Fe2O3 mol% with average crystallite size of 74 nm. Hexagonal iron phosphate FePO4 phases appeared with Fe2O3 exceeded 30 mol%. The high-temperature conductivity is well explained by polaronic hopping conduction model. It is observed that in this system non-adiabatic hopping conduction is present. The longitudinal optical phonon frequency (νο) and density of state N(EF) of the prepared glass and corresponding glass–ceramics are reasonable for the localized states.

Preparation and Properties of Lead-Iron-Phosphate Nuclear Waste Glasses

Lead-iron phosphate (LIP) glasses are a promising new waste form for safe immobilization of both high level defence and high level commercial radioactive waste for long term disposal. LIP glasses have several advantages such as lower aqueous corrosion rate, lower processing temperature, etc. The durability test for LIP glasses showed that the alkaline earth oxides BaO, SrO and CaO decrease the durability while PbO, Fe2O3 and CeO2 improves the corrosion resistance. For some LIP glass samples containing uranium the leach rates as calculated from BET surface areas were in the range of 8.2×10–4 to 4.3×10–3 g.m–2.h–1 at 90°C which is 1000 times lower than that of the borosilicate glasses. Thermal study shows that the glass transition temperature was in the range of 360°-400°C for the LIP glasses. IR studies show absorptions at 520, 1025, 1700, 2225 and 3450 cm–1. The observed IR and Raman scattering spectra are representative of a mixture of chain terminating Q1 species and chain forming Q2 species. From the radiotracer leaching studies the role of Ce4+ as good binder-modifier is established. The values of isomer shift in the Mössbauer spectra increases with increasing Fe2O3 content.

인산화/증류/고화의 일련공정을 이용한 LiCl-KCl 공융염폐기물 내 희토류 핵종 분리 및 고화

사용후핵연료 파이로프로세싱에서 발생하는 LiCl-KCl 공융염폐기물의 부피를 최소화하고 최종적으로 잔류하는 폐기물을 비교적 낮은 온도에서 안정한 형태로 고화하고자 희토류 핵종 염화물을 함유한 LiCl-KCl 공융염을 이용하여 인산화/증류 및 세라믹 고화의 일련공정을 수행하였다. LiCl-KCl 공융염 내 희토류 염화물은 혼합인산화제(<TEX>$Li_3PO_4-K_3PO_4$</TEX>)를 이용한 인산화 및 공융염 감압증류공정을 통하여 99% 이상을 인산화물 형태로 전환/분리할 수 있었고, 분리한 희토류 인산화물은 고화매질로서 LIP(Lead Iron Phosphate)를 이용하여 <TEX>$1,050^{\circ}C$</TEX>에서 균질하고 치밀한 형태의 고화체로 제조할 수 있었으며, 최종적으로 발생하는 방사성 폐기물 부피를 10% 이하로 감용할 수 있음을 확인하였다. Pyroporcessing of spent nuclear fuel generates a considerable amount of LiCl-KCl eutectic waste salt containing radioactive rare earth (RE) chlorides. In this study, a series of processes, which consist of a phosphorylation/distillation process and a solidification process, were performed to minimize volume of the LiCl-KCl eutectic waste salt and solidify a residual waste into a stable form at a relatively low temperature. Over 99wt% of RE chlorides in LiCl-KCl eutectic salt was converted and separated into <TEX>$REPO_4$</TEX> in the phosphorylation/distillation process using a mixture of <TEX>$Li_3PO_4-K_3PO_4$</TEX>. The separated <TEX>$REPO_4$</TEX> was solidified into a homogeneous and fine-grained form at <TEX>$1,050^{\circ}C$</TEX> using LIP(Lead Iron Phosphate) as a solidification agent. The final waste volume was reduced below about 10% through the series of the processes.

Physical properties of lead iron phosphate glasses containing Cr 2O 3

The influence of Cr 2O 3 on glass forming characteristics and physical properties of PbO–Fe 2O 3–P 2O 5 glasses has been investigated by Raman and Mössbauer spectroscopies, X-ray diffraction analysis (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM) and impedance spectroscopy. Glasses of the general composition xCr 2O 3–(28.3-x)PbO–28.7Fe 2O 3–43.0P 2O 5, 0 ≤ × ≤ 10, (mol%) were prepared by conventional melt-quenching technique. The compositions containing up to 4 mol% Cr 2O 3 formed fully amorphous samples and their Raman spectra show systematic increase in the fraction of orthophosphate Q 0 units with increasing Cr 2O 3 content and O/P ratio. On the other hand, compositions containing 8 and 10 mol% Cr 2O 3 partially crystallized during cooling and annealing to Fe 7(PO 4) 6, Fe 2Pb 3(PO 4) 4 and Cr 2Pb 3(PO 4) 4. A high tendency for crystallization of these melts is related to the high O/P (> 4) and Fe 2+/Fe tot (≈ 0.60) ratios. Electrical conductivity of xCr 2O 3–(28.3-x)PbO–28.7Fe 2O 3–43.0P 2O 5, 0 ≤ × ≤ 10, (mol%) compositions is independent of Cr 2O 3 and controlled entirely by the polaron transfer between Fe 2+ and Fe 3+ ions.

Colorimetric study on the redox number of P2O5–PbO–Fe2O3 glasses

Abstract Semi-conducting property of lead iron phosphate glasses is assumed to be due to the hopping process. Redox number of glass is usually determined by Mossbauer spectroscopy. However, the technique is limited by low sensitivity in lower concentration of iron ions. Neither is suitable for the traditional method since Fe2+ in the glass is apt to oxidize and results in the uncertainty of the concentration. In this paper, a colorimetric method was performed to study the redox number of the glasses. Sample solutions have been prepared by using a vanadate as an oxidizing inhibitor for the equilibrium of Fe2+/Fe3+ pairs. The V5+/V4+ couple, which is strongly acid-dependent, oxidizes the Fe2+ to Fe3+ in the highly acidic solution, and it is regenerated when the solution was adjusted to pH 5 from V4+ preservative. The measurement of the electric conductivity of the glasses has indicated the fact that, other than the concentration of the electric conducting carriers, redox number of the glass plays a significant role for the semi-conducting phosphate glasses. The method was validated by analyzing a mixture of ammonium iron (II) sulfate and/or ammonium iron (III) sulfate solutions and has been proved to be simple, accurate and reliable.

Studies of lead–iron phosphate glasses by Raman, Mössbauer and impedance spectroscopy

The effect of Fe2O3 content on electrical conductivity and glass stability against crystallization in the system PbO–Fe2O3–P2O5 has been investigated using Raman, XRD, Mössbauer and impedance spectroscopy. Glasses of the molar composition (43.3−x)PbO–(13.7+x)Fe2O3–43P2O5 (0⩽x⩽30), were prepared by quenching melts in the air. With increasing Fe2O3 content and molar O/P ratio there is corresponding reduction in the length of phosphate units and an increase in the Fe(II) ion concentration, which causes a higher tendency for crystallization. Raman spectra of the glasses show that the interaction between Fe sites, which is essential for electron hopping, strongly depends on the cross-linking of the glass network. The electronic conduction of these glasses depends not only on the Fe(II)/Fetot ratio, but also on easy pathways for electron hopping in a non-disrupted pyrophosphate network. The Raman spectra of crystallized glasses indicate a much lower degree of cross-linking since more non-bridging oxygen atoms are present in the network. Despite the significant increase in the Fe2O3 content and Fe(II) ion concentration, there is a considerable weakening in the interactions between Fe sites in crystalline glasses. The impedance spectra reveal a decrease in conductivity, caused by poorly defined conduction pathways, which are result of the disruption and inhomogeneity of the crystalline phases that are formed during melting.

Layered Ordering of Vacancies of Lead Iron Phosphate Pb3Fe2(PO4)4.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Layered ordering of vacancies of lead iron phosphate Pb 3Fe 2(PO 4) 4

Lead iron phosphate Pb 3Fe 2(PO 4) 4 has been synthesized by solid state method and characterized by X-ray powder and electron diffraction, differential scanning calorimetry, Mössbauer and infrared spectroscopy. A structural model for Pb 3Fe 2(PO 4) 4 is proposed and is refined by the Rietveld method. The compound crystallizes in the monoclinic space group P 2 1 / c with a = 9.0065 ( 6 ) Å , b = 9.0574 ( 6 ) Å , c = 9.3057 ( 6 ) Å , β = 116.880 ( 4 ) ° , V = 677.10 ( 8 ) Å 3 , Z = 2 , R wp = 3.52 % , R p = 2.66 % . It exhibits a structure with a three-dimensional open framework. The 3D framework is formed by PO 4 tetrahedra and FeO 6 octahedra connected via common vertices. ¾ of cavities in the framework are occupied by lead and ¼ are vacant.

Structural features and properties of lead–iron–phosphate nuclear wasteforms

The structure and properties of vitreous and crystalline lead–iron–phosphate glasses containing up to 21 wt% of a simulated high level waste have been investigated using Fe-57 Mössbauer, X-ray diffraction and Raman spectroscopies. The Mössbauer spectra indicated that both Fe(II) and Fe(III) ions were present in all the samples. The Raman spectra for the glasses contained two dominant bands, which were characteristic of pyrophosphate groups, (P–O) stretching mode of P–O nonbridging oxygen at 1074 cm −1 and sym stretching mode of bridging oxygen at 760 cm −1, respectively. The chemical durability of glassy and crystallized samples was investigated by measuring their weight loss in distilled water at 90 °C for up to 32 days. The weight loss of the lead–iron–pyrophosphate wasteforms was up to 100 times less than that for window glass. X-ray diffraction patterns showed that FeSiO 3 and SiP 2O 7 phases are present in samples containing more than 14 wt% of the simulated nuclear waste.

Structural features of lead iron phosphate glasses

Lead iron–phosphate glasses were investigated for use as wasteform because of their improved chemical durability. There is a controversy if lead should or should not be used in iron phosphate glasses, and on the role of Fe in the inhibition of corrosion. The structure of the 43.3PbO·13.7Fe 2O 3·43P 2O 5 (mol%) glass, which has a dissolution rate in aqueous solution at 90 °C of 1.26×10 −9 g/cm −2 min −1, and the same O/P ratio, 3.5, as the lead-free 40Fe 2O 3·60P 2O 5 glass, was investigated. Glass samples were produced by melting batches of Fe 2O 3, PbO, and NH 4H 2PO 4 at 1100 °C for 1 h, and pouring the liquid into steel mold. Samples were annealed at 450 °C for 3 h. Some samples were crystallized by heating at 700 °C for 24 h. X-ray diffraction, Mössbauer, EPR, infrared, and Raman scattering spectroscopy were performed and compared to spectra obtained after crystallization. The crystalline phase Fe 2Pb(P 2O 7) 2 was identified after crystallization. The hyperfine parameters from the Mössbauer spectrum indicates that Fe 2+ and Fe 3+ ions are in octahedral coordination, and some of the Fe 3+ ions in the starting batch are reduced to Fe 2+ ions after melting. The infrared and Raman scattering spectra are representative of a mixture of chain-terminating Q 1 species and chain-forming Q 2 species. No Raman bands related to PO vibrations and Q 0 species were observed. From the EPR measurements it is concluded that all Fe 3+ ions are not constrained to central positions of tetrahedral and octahedral sites of the glass formers.

Cs immobilization by sintered lead iron phosphate glasses

Lead iron phosphate glass frits were obtained from a mixture of NH 4H 2PO 4, PbO and Fe 2O 3 melted in an induction furnace. After milling, the material was pressed in a die, sintered, and sintered a second time. Three amorphous X-ray diffraction halos were observed in samples produced from non-homogenized powders while two halos were observed from homogeneous ones. These halos were assigned different phosphate compounds. Sintered pellets were immersed in a CsCl aqueous solution and the absorption of Cs was determined by scanning electron microscopy. The crystallization temperatures and activation energies were determined by differential thermal analysis and by the Kissinger Method, respectively. The weight loss and atomic absorption were used to measure the dissolution rate in deionized water. The weight loss of sintered glasses was 3 × 10 −2 g/m 2 d after 28 days at 90°C. The homogenized samples have an improved corrosion resistance.

Lead Iron Phosphate Powders Produced by Melting and Fast Cooling

Lead iron phosphate glasses are potentially useful for nuclear waste immobilization, and others applications. Lead iron phosphate glass powders were obtained from a mixture of NH 4 H 2 PO 4 , PbO and Fe 2 O 3 melted in an induction furnace and fast cooled. After milling, the material was pressed in a die and finally sintered. The particle size distribution, specific surface area, density values and crystalline phases were determined. Three amorphous halos were observed with intensities depending on the particle size distribution, These halos were assigned to be from ferric metaphosphate (Fe(PO 3 ) 3 , lead orthophosphate Pb 3 (PO 4 ) 2 and lead metaphosphate Pb(PO 3 ) 2 compounds. It is proposed that ferric metaphosphate is the main compound on the surface of the particles and lead orthophosphate and lead metaphosphate are in the inner part of the particles. The milling process allows to exhibit these compounds which are then detected by the X-rays diffraction. Pre-sintered pellets were exposed to CsCl aqueous solution and the absorption of Cs has been determined by SEM. Crystallization temperatures were determined by thermal analyses, and it is noted that the maximum is displaced from 534 to 543°C for samples containing CsCl. The surface area was determined to be 29 cm 2 /g after milling.

Kintoreite, PbFe3(PO4)2(OH,H2O)6, a new mineral of the jarosite-alunite family, and lusungite discredited

AbstractKintoreite is a new lead iron phosphate mineral in the alunite-jarosite family, from Broken Hill, New South Wales, Australia. It is the phosphate analogue of segnitite and the iron analogue of plumbogummite. Kintoreite occurs as clusters and coatings of cream to yellowish green rhombohedral crystals up to 2 mm high and with the principal form {112}. The mineral also forms waxy, yellowish green globular crusts and hemispheres on other phosphate minerals. These associated species include pyromorphite, libethenite, rockbridgeite/dufrenite, apatite and goethite. Kintoreite formed during oxidation of primary ore rich in galena, in the presence of solutions with high P/(As + S) ratios. The mineral is named for the locality, the Kintore opencut, in which it is most common. A mineral closely resembling kintoreite in composition has also been found at several mines in Germany. Type material is preserved in the Museum of Victoria and the South Australian Museum.Electron microprobe analysis showed a nearly complete spread of compositions across the P-dominant portion of the segnitite-kintoreite series. The selected type specimen has an empirical formula of Pb0.97(Fe2.95Zn0.13Cu0.02)Σ3.10[(PO4)1.30(AsO4)0.39(SO4)0.18(CO3)0.11]Σ1.98(OH)5.45·0.74H2O, calculated on the basis of 14 oxygens and with all Fe trivalent. The simplified formula is PbFe3(PO4)2(OH,H2O)6. Kintoreite crystals are translucent with a vitreous to adamantine lustre, with globules appearing waxy. The streak is pale yellowish green and the Mohs hardness is ∼ 4. Crystals show good cleavage on {001} and are brittle with a rough fracture. The calculated density is 4.34 g cm−3. Kintoreite crystals are uniaxial negative with RIs between 1.935 and 1.955 and show light yellowish green to medium yellow pleochroism.The strongest lines in the X-ray powder pattern are (dobs, Iobs, hkl) 3.07(100) 113; 5.96(90)101; 3.67(60)110; 2.538(50)024; 2.257(50)107; 1.979(50)303; 1.831(40)220. The X-ray data were indexed on a hexagonal unit cell by analogy with beudantite, giving a = 7.325(1) Å, c = 16.900(3) Å, V = 785.3(5) Å3 and Z = 3. The probable space group is Rm, by analogy with beudantite and other members of the alunite-jarosite family. Powder X-ray diffraction data for several intermediate members suggest that the segnitite-kintoreite series may not represent ideal solid solution.During the study of kintoreite, part of the type specimen of lusungite from Zaïre was obtained and shown to be goyazite. The IMA's Commission on New Minerals and Mineral Names has voted to discredit lusungite as a species, and has approved the renaming of the ‘lusungite’ group as the segnitite group. However, as relationships between crystal structure, order-disorder and solid solution in the Pb-rich minerals of the alunite-jarosite family are not well documented, the nomenclatural changes resulting from this study should be seen as interim only.

Structural properties of lead-iron phosphate glasses by X-ray diffraction

The structural properties of lead-iron phosphate glasses have been investigated by X-ray diffraction in an attempt to understand the chemical and mechanical characteristics presented by lead metaphosphate glass as the result of the addition of iron oxide. Information on FeO bond lengths and coordination numbers was obtained by a comparison of radial distribution functions of glass samples containing iron oxide and of the iron-free glass matrix. Stable structural arrangements around Fe(III) atoms were detected, which could be responsible for the stabilizing effect of Fe 2O 3 on lead metaphosphate glass.

Structural relaxation dynamics of phosphate glasses: The effects of network topology on the glass transition

Scanning calorimetry measurements were made on a series of lead (( y)PbO + (1−y)P 2O 5, 0.3 < y < 0.55) and lead-iron phosphate glasses ((1− xPb(PO 3) 2 + ( x)Fe 2 O 3, 0 < x < 0.25) over a temperature range encompassing the glass transition. The apparent activation energy for structural relaxation, ΔH, determined for each composition from plots of the inverse of the glass transition temperature, T g vs. the log of the cooling rate, was found to increase with the metal-to-phosphorus ratio. The value of ΔH increased from 44 kcal/mol for P 2O 5 to 350 kcal/mol for a lead-iron phosphate glass with x = 0.25. The calorimetry data were analyzed using the Adam-Gibbs-Scherer model of the glass transition. This analysis suggests that these glasses undergo a transition from ‘strong’ to the ‘fragile’ glass regime as the metal-to-phosphorus ratio is increased. It is also shown that this transition may be related to the phase transition predicted by He and Thorpe for glasses with underconstrained networks. From scanning calorimetry data on P 2O 5, B 2O 3 and a lead-iron phosphate glass ( x = 0.15), the temperature dependence of the shear viscosity for each material above T g was calculated and compared with published viscosity data.

Leach Rates and Thermal Properties of Lead-Iron Phosphate Glass Waste Forms

Lead-iron phosphate (LIP) glasses loaded with a simulated high-level nuclear waste were studied on their leach rates and thermal properties. The obtained results showed that the phosphate glass matrix consisting of lead monoxide, phosphorus pentoxide and ferric oxide of 56:35:9w/0 is able to vitrify the waste, pretreated with formic acid to remove Zr, to about 15 w/0 at 950°C. The leach rate of the vitrified waste glass was in the order of 10−7 g/cm2.d at 110°C, which is low compared with that of the borosilicate glass waste form. Increasing the phosphorus pentoxide content of the matrix to higher than 35% enabled it to produce the glass form with the waste near 20 w/0 at 950°C, but this increase rendered the glass waste form more soluble than the former. Thermal properties such as thermal expansion coefficient, critical cooling rate for vitrification and temperatures of glass transition, softening and maximum rate of crystallization were measured and discussed. Removing Na ions from wastes improves consi...