Rare Earth Phosphates Research Articles

Synthesis and characterization of rare-earth doped aluminium phosphate glasses

Sodium aluminium phosphate (NAP) glass is a potential candidate for the immobilization of minor actinides (MA). The composition of the NAP glass 38Na2O–30Al2O3–32P2O5 (mol %) was found to be the optimal choice, through experimental trials and specimens of this glass containing 1, 5, 10 and 15 wt% of the rare-earths (Ce, Pr, Nd and Gd-as surrogates for MA) were prepared by the melt quench technique. All these samples were X-ray amorphous, and were found to contain (PO4)−2 Q1 and (PO4)−1 Q2 units. Both Al2O3 and rare-earths were found to modify the structure of the phosphate glass significantly. Al2O3 plausibly acts as a network former at higher concentrations. The melting point, glass transition temperature, viscosity, Angell thermal stability and glass forming ability of these glasses increase with the concentration of the dopants, while their fragility decreased. Absolute values of the heat capacity of these glasses (Cp) as well as the attendant change in the heat capacity during the glass transition ΔCp showed an increase up to 5 wt % doping and a decrease subsequently when the concentration of the dopants were increased up to 15 wt%. Glasses containing 10 and 15 wt% dopants show sharper crystallization peaks while the crystallization is less pronounced in the rest of the glass samples. The rare-earth cations improve the strength of the glass when doped up to 5 wt%, beyond which the rigidity of the structure begins to fall. The networking due to complexation diminishes and leads to weaker chains resulting in the glasses with higher concentration of the rare-earths modifiers. These first results on the dependence of the structure and thermal properties of the NAP glass 38Na2O–30Al2O3–32P2O5 (mol%) doped with rare-earth reported here show that this glass could serve as a suitable matrix for immobilizing rare earths and minor actinides.

Structural stability of REE-PO4 (REE = Sm,Tb) under swift heavy ion irradiation

Rare earth element (REE) phosphates are an attractive host matrix for long-lived radionuclides from nuclear waste because of the radiation tolerance exhibited by naturally occurring REE phosphate specimens. Here we show that SmPO4 (monazite structure) and TbPO4 (xenotime structure) exhibit a similar amorphization response to swift heavy ion irradiation despite different starting structures. SmPO4 and TbPO4 were irradiated with 1.1 GeV Au ions and analyzed using synchrotron-based X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The radiation response of the phosphates was evaluated by extracting the amorphous fraction at each irradiation fluence, and a single-impact model was used to determine the amorphous cross section and track diameter. Amorphization within individual ion tracks was confirmed using head-on TEM imaging, and the amorphous track size agreed with the value deduced by XRD analysis. Raman measurements were performed to qualitatively confirm the ion-induced crystalline-to-amorphous transformation which proceeds similarly for both phosphates.

Novel photo-responsive composite fibers fabricated by facile wet-spinning process for UV detection and high-level encryption

Fibers with reversible optical properties under light irradiation are highly demanded in diverse applications such as information storage, wearable camouflage and multicolor displays. However, conventional photo-responsive fibers are not able to be detected in both daylight and darkness limiting their application as smart materials in intelligent systems. Herein, the photo-responsive fibers detectable in both daylight and darkness are fabricated by a facile wet-spinning process. By employing spiropyran dyes and two types of rare-earth phosphors (SrAl2O4:Eu2+, Dy3+, Sr2MgSi2O7: Eu2+, Dy3+), the prepared fibers exhibit excellent and swift reversible photochromic properties. Furthermore, the fibers emit greenish-blue light with long afterglow for a broad range of excitation wavelengths from visible light to ultraviolet (UV) light. Capitalizing the intriguing photo-responsive features, the developed fibers offer applications in wearable and visualized UV detectors as well as high-level information encryption.

Implications of Magnetic Properties in the Concentration and Distribution of REEs in Beach Placer Monazites: A Case Study from Chhatrapur Coast, Odisha

Abstract The concentration of monazite, a rare earth and thorium phosphate, in the heavy mineral-bearing sands of Chhatrapur coast varies from 0.09 to 0.16%. Under the microscope, monazite displays color variation from colorless to various shades of yellow, green and brown. The color variation is further reflected in the chemistry of individual grains. Such monazites of distinct colors and different chemistry also show variation in their paramagnetic properties. Representative detrital monazites separated under varied magnetic field strength were analysed for their rare earth elements, Th and U content. The electron probe micro analysis (EPMA) data indicate that monazites separated under low magnetic field strength (separated at 0.80 amps) are characterized by their higher Nd, Sm, HREE, Y and U as well as low Th content, whereas those separated at 1.10 amps contain low Nd, Sm, HREE with negligible Y and U content as well as higher Th content. The wider variation in the concentration of different rare earths in varied magnetic field strength is a function of varied magnetic susceptibility of individual elements. Hence, the physical method for separation of monazite using magnetic properties may facilitate to segregate the monazites of a particular chemical composition with respect to their constituent elements like U, Th and rare earths based on their magnetic properties.

Prospectivity mapping of carbonatite-associated iron oxide deposits using an integration process of ASTER and Sentinel-2A multispectral data

ABSTRACT Carbonatites and associated rocks are commonly known to host precious commodities, including rare earth elements (REE), niobium, and phosphates. They form ring-shaped complexes frequently found as small occurrences in hard-to-reach areas, making their exploration a challenging task using conventional methods. Remote sensing has been increasingly regarded as a time- and cost-saving method to map and identify new potential zones, meeting the growing need for mineral resources. In this study, we use multispectral data by combining information from ASTER and Sentinel 2A sources to delineate and map carbonatite-associated REE- and Nb-enriched iron oxide deposits. The Moroccan Oulad Dlim massif, at the NW margin of the west African craton, where carbonatite occurrences are reported, was selected as a study area. A fuzzy gamma approach was adopted to combine information from several image processing techniques, including mineral indices, principal component analysis (PCA) and minimum noise fraction (MNF). A concentration-area (C-A) fractal model is applied together with the prediction-area (P-A) plot for objective anomalies classification and prediction ability assessment for each fuzzy integrated map. Subsequently, a prospective map that predicts and defines potential areas was produced through the integration of Sentinel- and ASTER-derived evidential maps. Validation was carried out via field surveys coupled with in-situ portable X-Ray Fluorescence analysis and laboratory mineralogical characterization. The Results were consistent with field data, reaching a prediction rate of 90%. They reveal the importance of the investigated structures as potential sites for REE, Nb, and phosphates. These outcomes are encouraging and provide evidence that data fusion (ASTER-Sentinel 2A) is an effective and helpful approach for geological exploration programmes.

Quantum efficiency of europium doped LaPO4 phosphors for UV sensing applications

The radiation conversion phenomenon is used for UV sensing applications with rare earth doped phosphors. This paper presents the results of structural and optical measurements of undoped and europium doped LaPO4 phosphors. LaPO4 phosphors with 1% mol, 2% mol, and 5% mol of europium were fabricated by the co-precipitation method. The effect of Eu3+ concentrations on the luminescence characteristics under UV LED excitation was investigated. The maximum quantum efficiency of luminescence (c.a. 82%) was obtained in sampled doped with 5% of europium. Full Text: PDF ReferencesM. Runowski, "Nanotechnologia – nanomateriały, nanocząstki i wielofunkcyjne nanostruktury typu rdzeń/powłoka", Chemik 68, 9, 766-775 (2014). DirectLink J. Zhou, J.L. Leano Jr., Z. Liu, D. Jin, K.-L. Wong, R.S. Liu, et al., "Impact of Lanthanide Nanomaterials on Photonic Devices and Smart Applications", Small 14, 1801882 (2018). CrossRef Z. Li, Y. Zhang, G. Han, "Lanthanide-Doped Upconversion Nanoparticles for Imaging-Guided Drug Delivery and Therapy", Springer Series in Biomater. Sci. Eng. 6, 139-164, (2016). CrossRef M. Lin, Y. Zhao, S. Wang, M. Liu, Z. Duan, Y. Chen, et al., "Recent advances in synthesis and surface modification of lanthanide-doped upconversion nanoparticles for biomedical applications", Biotechnol. Adv. 30, 1551-1561 (2012). CrossRef H. Su, Y. Nie, H. Yang, D. Tang, K. Chen, T. Zhang, "Improving the thermal stability of phosphor in a white light-emitting diode (LED) by glass-ceramics: Effect of Al2O3 dopant", J. Eur. Ceram. Soc. 38, 2005-2009 (2018). CrossRef J. Huang, X. Hu, J. Shen, D. Wu, C. Yin, R. Xiang, et al., "Facile synthesis of a thermally stable Ce3+:Y3Al5O12 phosphor-in-glass for white LEDs", Cryst. Eng. Comm 17, 7079-7085 (2015). CrossRef R. Zhang, H. Lin, Y. Yu, D. Chen, J. Xu, Y. Wang, "A new-generation color converter for high-power white LED: transparent Ce3+:YAG phosphor-in-glass", Laser Photon. Rev. 8, 158-164 (2014). CrossRef B. Zheng, Y. Bai, H. Chen, H. Pan, W. Ji, X. Gong, et al., "Near-Infrared Light-Excited Upconverting Persistent Nanophosphors in Vivo for Imaging-Guided Cell Therapy", ACS Appl. Mater. Interfaces 10, 19514 (2018). CrossRef J. Qiao, G. Zhou, Y. Zhou, Q. Zhang, Z. Xia, "Divalent europium-doped near-infrared-emitting phosphor for light-emitting diodes", Nature Communications 10 (1), 5267 (2019). CrossRef V. Singh, A. Kumar, C. Mehare, H. Jeong, S. Dhoble, "UV/VUV excited photoluminescence of Tb3+ doped LaPO4 green emitting phosphors for PDP applications", Optik 206, 163733 (2020). CrossRef G. Han, Y. Wang, C. Wu, J. Zhang, "Hydrothermal synthesis and vacuum ultraviolet-excited luminescence properties of novel Dy3+-doped LaPO4 white light phosphors", Mat. Res. Bull. 44 (12), 2255-2257 (2009). CrossRef K. S. Gupta, P. S. Ghosh, M. Sahu, K. Bhattacharyya, R. Tewari, V. Natarajan, "Intense red emitting monoclinic LaPO4:Eu3+ nanoparticles: host–dopant energy transfer dynamics and photoluminescence properties", RSC Adv. 5, 58832-58842 (2015). CrossRef

Structural and surface studies of luminescent Ca/Eu phosphate nanomaterials: From the bulk to surface features

Three luminescent Eu-containing phosphate materials (Ca-doped europium phosphate monohydrate, Eu-doped carbonated-apatite, and europium phosphate monohydrate) were prepared and analyzed on the level of bulk structure and surface properties and compared to the biomimetic non-luminescent counterpart hydroxyapatite. Europium-containing phosphate materials exhibited nanosized dimensions but different luminescence emissions and luminescence lifetimes depending on their crystalline structures (i.e., lanthanide phosphate or apatites) and chemical composition. The introduction of Eu in the crystal lattice leads to a notable decrease in the overall Lewis acidity of the surface cationic sites detected by CO probing. Further, the mixed Eu/Ca-containing materials surfaces were found to be very similar to the reference hydroxyapatite in terms of water adsorption energy, while the pure europium phosphate resulted to have the notably higher energy values of direct interaction of water molecules with the surface cations with no detected propagation of this effect towards water overlayers.

Geology, geochemistry, and genesis of REY minerals of the late Cretaceous karst bauxite deposits, Zagros Simply Folded Belt, SW Iran: Constraints on the ore-forming process

The present study focuses on the geochemistry and occurrence of REY (rare earth elements and yttrium)-bearing minerals in the Late Cretaceous karst bauxite deposits in the central part of the Zagros Simply Fold Belt (ZSFB), SW Iran. The ore bodies comprise a series of individual pods and/or contiguous lenses that occur as infills of deep karst cavities, depressions, and fractures within the upper neritic carbonates of the Cenomanian–Turonian Sarvak Formation. Karst bauxites from the ZSFB show, overall, the same mineral components, which consists of boehmite, hematite (commonly occurring as Al-rich), anatase, and kaolinite, with lesser amounts of diaspore, goethite, chamosite, rutile, and zircon. Among minor constituents, single crystals rich in rare earth elements (REEs) occur mainly in the form of authigenic REY fluorocarbonate, phosphate, and oxide minerals (bastnasite, parisite, rhabdophane, churchite and cerianite). Some textural features, such as spheroidal concretions, pisoids with cortexes lacking radial and circular fractures, growth of simple cortex around earlier pisoids, and pelitomorphic matrix suggest the ores are mostly autochthonous in origin. R-mode factor analysis revealed several significant interelemental relationships including: (i) significant and positive weightings for TiO2, Al2O3, Cr2O3, Ni, Zr, Nb, Hf, Ta, W, and Th, and a significant, negative weighting for SiO2 represent a later bauxitization stage involving silica depletion under drier conditions, promoting formation and stability of a range of minerals including detrital minerals and Al and Ti oxyhydroxides which also control, through scavenging, cations of first-row transition metals such as Ni2+ and Cr6+; (ii) Supergene conditions, mainly acidic pH, probably played an efficient role in the formation of secondary REE-rich phosphates and Ga-hydroxide; (iii) similar and meaningful weightings for U and V suggest that the redox environment would be most important in controlling the U and V mineral phases; and (iv) the scandium co-variance with Fe2O3 represents the control exerted by iron oxy-hydroxides on the critical metal Sc. In the ZSFB bauxites, the most frequent authigenic REE-bearing minerals are light REE (LREE) fluorocarbonates of the bastnaesite group that forms a solid solution series between end members parisite [CaCe2(CO3)3F2] and bastnäsite (CeCO3F). The mode of occurrence of bastnäsite-Ce and parisite-Ce suggests that cerium as fluoride and/or carbonate–fluoride complexes were readily leached by acidic downward solutions and finally precipitated on the geochemical barrier of the carbonate bedrock under alkaline and reducing conditions. Rhabdophane [(Ce, La) PO4·H2O] as an LREE phosphate mineral appears in two generations with different chemical compositions, an early one as irregular and/or acicular particles within the cavities and a later one along the margin of a goethite microvein that cuts the pelitomorphic matrix. Cerianite (CeO2) occurs mainly as sub-micrometer to micrometer grains in the porous aggregates of the aphanitic matrix and as microdomains or microveins that coexist with Al-oxyhydroxide and goethite. Cerianite precipitation may occur due to the predominance of acidic/oxidizing conditions and the dissolution of Ce-rich fluorocarbonates in the bauxitic profile, respectively. The only heavy REE (HREE) phosphate mineral within the ZFSB bauxite deposits is churchite[Y(PO4)·2(H2O)] that forms as single euhedral crystals at the core of the sub-spheroidal structures under an acidic condition.

Dual-field responsive polymer-dispersed liquid crystal films with polymer spacer columns and fluorescent properties

ABSTRACT Polymer dispersed liquid crystal (PDLC) films with polymer spacer columns were prepared by photomask stepwise polymerisation method. The effects of crosslinker content and liquid crystal (LC) content on the morphologies of polymer spacer columns and electro-optical properties of PDLC films were investigated. Due to the difference of crosslink density and system viscosity, the polymer spacer columns exhibit different morphologies and the electro-optical properties of PDLC films are also altered. Based on the above, the PVA coatings loaded with rare earth phosphor were introduced into PDLC films. The influences of rare earth phosphor concentration on the fluorescent and electro-optical properties of PDLC films were studied. Also, it was found that the UVaging resistance of PDLC films was enhanced because of the loading of rare earth phosphor absorbing UV light. Therefore, the successful preparation of PDLC films with polymer spacer columns and reversible fluorescence properties opens new possibilities for expanding the flexible display applications of PDLC.

Structural and magnetic properties of churchite-type REPO4·2H2O materials

The structural and magnetic properties of churchite-type REPO4·2H2O (RE ​= ​Gd to Lu) materials (low-temperature polymorph of the rare-earth phosphate family) are reported. The materials were synthesized at low temperatures (4 ​°C) using a precipitation method and the long-range and local structures were determined using powder XRD and XANES. The churchite materials crystallize in the monoclinic system (Space group – C2/c) and adopt a 2D layered structure with water occupying the interlayer regions. The churchite materials were found to transform to the xenotime structure at 300 ​°C. DC magnetization experiments reveal the absence of long-range magnetic ordering between 300 and 1.8 ​K. The effective magnetic moments (μeff) are similar to those of the free RE (RE ​= ​Gd, Tb, Dy, Ho, Er) ions.

A Kinetic Isotope Effect in the Formation of Lanthanide Phosphate Nanocrystals.

Mechanisms of nucleation and growth of crystals are still attracting a great deal of interest, in particular with recent advances in experimental techniques aimed at studying such phenomena. Studies of kinetic isotope effects in various reactions have been useful for elucidating reaction mechanisms, and it is believed that the same may apply for crystal formation kinetics. In this work, we present a kinetic study of the formation of europium-doped terbium phosphate nanocrystals under acidic conditions, including a strong H/D isotope effect. The nanocrystal growth process could be quantitatively followed through monitoring of the europium luminescence intensity. Hence, such lanthanide-based nanocrystals may serve as unique model systems for studying crystal nucleation and growth mechanisms. By combining the luminescence and NMR kinetics data, we conclude that the observed delayed nucleation occurs due to initial formation of pre-nucleation clusters or polymers of the lanthanide and phosphate ions, which undergo a phase transformation to crystal nuclei and further grow by cluster attachment. A scaling behavior observed on comparison of the H2O and D2O-based pre-nucleation and nanocrystal growth kinetics led us to conclude that both pre-nucleation and nanocrystal growth processes are of similar chemical nature.

Encapsulation of 67Cu therapeutic radiometal in luminescent lanthanide phosphate core and core-shell nanoparticles

Copper-67 (67Cu) has physical characteristics useful for both therapy and imaging. However, its applicability has been hindered by the complexity of obtaining large quantities of a product with high specific activity. With the advancement of 67Cu production methods, suitable radioisotope carriers are sought. Lanthanide phosphate nanoparticles have demonstrated their multifunctional characteristics for biomedical applications and, more recently, their potential in radiopharmaceuticals. Thus, we produced luminescent lanthanide phosphate nanoparticles with core and core-shell structures, incorporating 67Cu during their synthesis. The nanoparticles exhibited hexagonal crystalline structure and spherical morphology with sizes below 6 nm. The luminescent colloidal suspensions evidenced the characteristic 5D0-7FJ for Eu3+, providing the red color under UV light. A radiochemical yield of 67Cu >95% was obtained with both core and core-shell LaPO4:Eu. The core-shell nanoparticles reduced the release of 67Cu by a factor of ∼2 over that from the core, which continuously decreased with time. Multifunctional LnPO4 nanoparticles have the potential to be used as a carrier of single or multiple radioisotopes to enhance image-guided targeted nano-radiopharmaceutical therapy.

Influence of the Alkali-promoted phase transformation in monazite for selective recovery of rare-oxides using deep eutectic solvents

• High temperature formation of Ce 1 - x Ln x O 2 - x / 2 solid solutions has been demonstrated. • Electrochemical activity of pure rare earth oxides in the DES Ethaline has been proven. • 23.85% Nd 2 O 3 in a 0.1 mol/L glucose solution in Ethaline was dissolved. • No dissolution was reported for pure CeO 2 , La 2 O 3 and PrO 2 /Pr 2 O 3 . • Dissolution of Ce 1 - x Ln x O 2 - x / 2 formed in roasting was not possible because of its inert behaviour. The physico-chemical changes occurring during the high-temperature phase transformation of monazite in the presence of Na 2 CO 3 at 1000 °C for 2 h duration at monazite: Na 2 CO 3 ratios between 1.0 and 5.0, were investigated. The formation of sodium lanthanide phosphates was prevalent above a monazite:alkali ratio of 2, however, below this ratio, the dephosphorization of monazite as Na 3 PO 4 and Ce 1 - x Ln x O 2 - x / 2 solid solutions occur offering unique selectivity for rare-earth oxide separation from the mineral matrix. Cyclic voltammetry of pure CeO 2 , La 2 O 3 , Nd 2 O 3 , and PrO 2 /Pr 2 O 3 was carried out in the deep eutectic solvent Ethaline (1:2 mixture of choline chloride and ethylene glycol) proving the electrochemical activity of these oxides. Electrodissolution of pure oxides and water-leached monazite after high-temperature reaction with a ratio of 1:1 was carried out in a 0.1 mol/L glucose solution in Ethaline showing a preferential solubility of 23.85% for pure Nd 2 O 3 . In contrast, pure oxides of CeO 2 , La 2 O 3 and PrO 2 /Pr 2 O 3 were found to be insoluble. We also observed that electrodissolution of the water leached monazite was not possible because of the inert behaviour of Ce 1 - x Ln x O 2 - x / 2 solid solutions. Avoiding cerium oxidation during the high-temperature process will lead to a method for further selectivity for rare-earth oxide processing using staged electro-chemical winning of oxides.

Synthesis and structural investigation of churchite-type REPO4·2H2O (RE = Y, Gd, Dy) nanocrystals

Churchite-type REPO4·2H2O (RE ​= ​Gd to Lu & Y) materials are a metastable polymorph of the rare-earth phosphate family and adopts a 2D layered structure with the water molecules occupying the interlayer regions. The synthesis and structural properties of churchite materials are not well-studied in comparison to those of other polymorphs of the rare-earth phosphate family and this article aims to address this aspect by carrying out a detailed synthetic and structural investigation of churchite-type REPO4·2H2O (RE = Y, Gd, Dy) materials. Phase-pure REPO4·2H2O materials were synthesized via precipitation method at temperatures ranging from room temperature (~22 °C) to 50 °C. The microstructure of these materials was determined using Optical microscopy, SEM, and TEM. Microstructural analysis using optical microscopy and SEM indicated that the REPO4·2H2O materials appear as needle like particles but in reality are agglomerates of single crystal nanorods as revealed by TEM analysis. The effect of temperature on their structure was determined using TGA, DSC, and ex-situ XRD. TGA-DSC results show that the interlayer water is removed from the churchite structure via an endothermic process in the 250° - 300 ​°C range. Ex-situ XRD experiments reveal that the churchite structure is unstable upon removal of water and undergoes a structural transformation to a thermodynamically stable xenotime (REPO4) structure at temperatures exceeding 200 ​°C.

Selective preparation of samarium phosphates from transition metal mixed solution by two-step precipitation

ABSTRACT Samarium-cobalt alloys are used as materials for powerful magnets with relatively high Curie temperatures. Samarium is a valuable and expensive material because it is one of a group of rare earth elements. In order to utilize this rare earth resource in a sustainable society, it is necessary to recover, reuse, and recycle rare earth elements. With this in mind, a new process for recovering neodymium phosphate from neodymium-iron mixed aqueous solutions has recently been reported, avoiding the difficulties reported with conventional methods. Given that rare earth phosphates are a major component of rare earth ores, this new process was proposed to recover them as phosphates. In this method, neodymium phosphate was selectively precipitated from a neodymium-iron mixture in a two-step process with an adjusted pH value. In this study, we attempted to selectively precipitate samarium phosphate from a mixed solution of transition metals using this two-step precipitation method. The advantage of this method is that the samarium compound can be separated from other metal salts without the use of high temperatures or special equipment. Optimal conditions were determined by evaluating the precipitates by molar ratio, color hue, UV-visible reflectance spectra, X-ray diffraction, and infrared spectroscopy of the precipitates obtained. In Step 1, the pH was adjusted using sodium hydroxide to remove cobalt, iron, and copper hydroxides other than samarium. In Step 2, after adding phosphoric acid, the pH was adjusted so that a precipitate of samarium phosphate was formed.

Zeolitic Imidazolate Framework 67-Derived Ce-Doped CoP@N-Doped Carbon Hollow Polyhedron as High-Performance Anodes for Lithium-Ion Batteries

Zeolitic Imidazolate Framework 67 (ZIF-67) and its derivates have attracted extensive interest for lithium-ion batteries (LIBs). Here, Cerium-doped cobalt phosphide@nitrogen-doped carbon (Ce-doped CoP@NC) with hollow polyhedron structure materials were successfully synthesized via ionic-exchange with Co and Ce ions using the ZIF-67 as a template followed with a facile low-temperature phosphorization treatment. Benefitting from the well-designed hollow polyhedron, steady carbon network, and Ce-doping structural merits, the as-synthesized Ce-doped CoP@NC electrode demonstrated superior performance as the anode in LIBs: a superior cyclability (400 mA h g−1 after 500 cycles) and outstanding rate-capability (590 mA h g−1, reverted to 100 mA g−1). These features not only produced more lithium-active sites for LIBs anode and a shorter Li-ion diffusion pathway to expedite the charge transfer, but also the better tolerance against volume variation of CoP during the repeated lithiation/delithiation process and greater electronic conductivity properties. These results provide a methodology for the design of well-organized ZIFs and rare earth element-doped transition metal phosphate with a hollow polyhedron structure.

Local structures of rare earth phosphate minerals by NMR

31P solid state NMR studies combined with DFT calculations were conducted over a chosen series of rare earth element phosphates (REEPO4s), selected on the basis of the size and magnetic properties of REEs (La, Sm, Lu and Yb). PXRD analysis revealed the presence of rhabdophane (La, Sm), monazite (La) and xenotime (Lu, Yb) phases of these phosphate compounds. The direct excitation and cross-polarization 31P NMR studies together with calculations confirmed the PXRD results for the abovementioned bulk structures, but also revealed presence of several local phosphorus environments on surfaces. NMR is sensitive to the atomic level local interactions, and we were able to show that the combination of experimental and theoretical NMR methods can provide information unavailable with other methods. Due to the distinct coordination of the water molecules to crystal surfaces with different Miller plane cleavages, we were able to identify from the NMR spectra the surface structures of the studied minerals. This adds to the knowledge of the bulk structures of REE phosphates and provides preliminary data for studies on coordination of various ligands on REE phosphate surfaces. This combination of experimental and computational methods can further be used for studies on surface chemistry, important for applications in catalysis and extraction of REEs from the minerals.

Facile hydrothermal synthesis of rare earth phosphate for boosting hydrogen evolution reaction

The water electrolysis process has attracted great attention due to the production of high energy density pure hydrogen. However, the involved cell reactions in this process such as hydrogen and oxygen evolution reactions are kinetically sluggish and demands high input energy to accelerate the rate of these reactions. Therefore, the development and application of efficient electrocatalyst is essential for hydrogen evolution reaction (HER) as well as oxygen evolution reaction (OER). In the present work, we have successfully synthesized two rare earth phosphates through the hydrothermal route and used as a catalysts towards HER in an acidic medium. The rare earth phosphate PrPO 4 exhibits better catalytic activity than YPO 4 catalyst. The overpotential of PrPO 4 , YPO 4 and standard Pt/C were found as 147, 484.3 and 58 mV vs. reversible hydrogen electrode, respectively, to reach current density 10 mA·cm −2 and corresponding Tafel slopes were found as 107.58, 118.73 and 80.89 mV decade −1 , respectively in 0.5 M H 2 SO 4 . The catalytic activity of PrPO 4 (472.83 mA·cm −2 ) overcome standard Pt/C (179.60 mA·cm −2 ) at high overpotential 450 mV vs. reversible hydrogen electrode. The prepared PrPO 4 shows efficient electrocatalytic activity towards HER in acidic medium because it possess high BET surface area, large ECSA value and small charge transfer resistance than YPO 4 . • Hydrothermal synthesis of rare earth phosphates and explored HER performance. • As prepared PrPO 4 exhibits good catalytic activity towards HER in 0.5 M H 2 SO 4 . • The overpotential 147 mV to get 10 mA·cm −2 and Tafel slope 107.58 mV decade −1 . • The efficient PrPO 4 followed Volmer-Heyrovsky mechanism for HER.

Inorganic halide perovskites for lighting and visible light communication

Inorganic halide perovskites (IHPs) have received substantial attention due to their unique optoelectronic properties. Among all the intriguing performance, the efficient luminescence of IHPs enables the practical application of white light-emitting diodes (WLEDs) for lighting. During the last decade, IHP-based white lighting sources with a high luminesce and a broad color gamut have been developed as strong competitors to conventional and classic WLEDs based on rare-earth phosphors and blue LED chips. Thus, it inspires us to give an overview of the emerging progress of IHP WLEDs that can function as lighting sources. Here, in this review, the generation of luminescent properties and white light in IHPs are first presented. Then, both photoluminescence and electroluminescence WLEDs with IHPs emitters, including both lead-based and lead-free IHPs, are synthetically discussed to exhibit their advantages. Furthermore, the efforts on the optical performance enhancement of IHPs in WLEDs are demonstrated and summarized. Apart from WLEDs, visible light communication based on IHPs featuring efficient luminescence is proposed to highlight their promising potential in lighting communication. Finally, some perspectives on the evolution and challenges are described, followed by an inspirational outlook on their future development.

MxLa1–xSiO2–yNz (M = Ca/Sr/Ba): Elucidating and Tuning the Structure and Eu2+ Local Environments to Develop Full-Visible Spectrum Phosphors

The local environments of rare-earth activators have profound effects on the luminescent properties of phosphors. Here, we elucidate the crystal structure of the LaSiO2N phosphor host using a combination of density functional theory calculations and synchrotron X-ray diffraction. We determine that LaSiO2N crystallizes in the monoclinic C2/c instead of the hexagonal P6̅c2 space group. To improve the luminescence performance, divalent cations M (M = Ca/Sr/Ba) were introduced into LaSiO2N to eliminate Eu3+. A family of apatite M1+xLa4–xSi3O13–x/2:Eu2+ (x ∼ 1.5, M = Ca/Sr/Ba) phosphors was further developed with unprecedented ultra-broadband (290 nm) emission spectra and excellent thermal stability. Detailed local environment investigations reveal that the formation of oxygen vacancies within and beyond the first-shell environment of Eu2+ is responsible for the redshift and broadening of the emission spectra via geometrical alteration of the Eu2+ local environment. This work provides new insights for understanding and optimizing the luminescence of rare-earth phosphors.