Phosphorous Acid and Urea: Valuable Sources of Phosphorus and Nitrogen in the Hydrothermal Synthesis of Ammonium-Thorium Phosphates

Salvadó, Miguel A.; Pertierra, Pilar; Bortun, Anatoly I.; Trobajo, Camino; Garcı́a, José R.

doi:10.1021/ic800818c

Cited by 21 publications

(20 citation statements)

References 25 publications

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“…The NH 4 Ce 2 (PO 4 ) 3 phase is also worthy of note, as only a few M I M IV 2 (PO 4 ) 3 phases are known where M I = NH 4 + . To the best of our knowledge, the known representatives of such phases include the ammonium‐zirconium phosphates described by Clearfield et al in 1984 and the ammonium‐thorium phosphates obtained by Salvado et al in 2008 , . At the same time, similar potassium containing compounds have been known since 1889, while potassium and ammonium have very close ionic radii (1.51 and 1.54 Å for coordination number 8, respectively).…”

Section: Resultsmentioning

confidence: 96%

“…Our findings demonstrate the first example of a cerium phosphate [NH 4 Ce 2 (PO 4 ) 3 ] isostructural to M I R IV 2 (PO 4 ) 3 (R = actinide). For example, recently reported thorium‐ammonium phosphate, NH 4 Th 2 (PO 4 ) 3 (monoclinic system, space group C 2/ c , unit cell parameters: a = 17.7238(5) Å, b = 6.90676(12) Å, c = 8.15603(32) Å, β = 102.1047(26)°) possesses the same structure. The NH 4 Ce 2 (PO 4 ) 3 phase is also worthy of note, as only a few M I M IV 2 (PO 4 ) 3 phases are known where M I = NH 4 + .…”

Section: Resultsmentioning

confidence: 98%

“…According to our data, the thermal decomposition behavior of NH 4 Ce 2 (PO 4 ) 3 and NH 4 Th 2 (PO 4 ) 3 were completely different. The latter possessed extremely high thermal stability and decomposes almost in one stage above 700 °C to form β‐Th 4 (PO 4 ) 4 (P 2 O 7 ) . In contrast, the thermal decomposition of NH 4 Ce 2 (PO 4 ) 3 began only at ca .…”

Section: Resultsmentioning

confidence: 99%

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Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

et al. 2019

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

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Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

et al. 2019

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“…10 Salvado et al reported a series of such hydrated phosphates with K, Rb, Cs, and NH 4 ions and investigated the detailed crystal structure from powder XRD studies. 11,12 The crystal structures of these hydrated phosphates have been explained by either an orthorhombic (Imma) or a tetragonal (I4 1 /amd) lattice where the distorted cubic CeO 8 and tetrahedral PO 4 units form the building blocks and the H 2 O and M + ions are occupied in the tunnels formed by these units. 11,12 Differential thermal analysis studies of Xu et al on hydrothermally prepared K 2 Ce(PO 4 ) 2 H 2 O indicated a dehydrated phase at higher temperature (HT) which undergoes a phase transition before its decomposition.…”

Section: Introductionmentioning

confidence: 99%

Phase Transformation, Vibrational and Electronic Properties of K₂Ce(PO₄)₂: A Combined Experimental and Theoretical Study

Bevara

Mishra

Patwe³

et al. 2017

Inorg. Chem.

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Herein we report the high-temperature crystal chemistry of KCe(PO) as observed from a joint in situ variable-temperature X-ray diffraction (XRD) and Raman spectroscopy as well as ab initio density functional theory (DFT) calculations. These studies revealed that the ambient-temperature monoclinic (P2/n) phase reversibly transforms to a tetragonal (I4/amd) structure at higher temperature. Also, from the experimental and theoretical calculations, a possible existence of an orthorhombic (Imma) structure with almost zero orthorhombicity is predicted which is closely related to tetragonal KCe(PO). The high-temperature tetragonal phase reverts back to ambient monoclinic phase at much lower temperature in the cooling cycle compared to that observed at the heating cycle. XRD studies revealed the transition is accompanied by volume expansion of about 14.4%. The lower packing density of the high-temperature phase is reflected in its significantly lower thermal expansion coefficient (α = 3.83 × 10 K) compared to that in ambient monoclinic phase (α = 41.30 × 10 K). The coexistences of low- and high-temperature phases, large volume discontinuity in transition, and large hysteresis of transition temperature in heating and cooling cycles, as well as drastically different structural arrangement are in accordance with the first-order reconstructive nature of the transition. Temperature-dependent Raman spectra indicate significant changes around 783 K attributable to the phase transition. In situ low-temperature XRD, neutron diffraction, and Raman spectroscopic studies revealed no structural transition below ambient temperature. Raman mode frequencies, temperature coefficients, and reduced temperature coefficients for both monoclinic and tetragonal phases of KCe(PO) have been obtained. Several lattice and external modes of rigid PO units are found to be strongly anharmonic. The observed phase transition and structures as well as vibrational properties of both ambient- and high-temperature phases were complimented by DFT calculations. The optical absorption studies on monoclinic phase indicated a band gap of about 2.46 eV. The electronic structure calculations on ambient-temperature monoclinic and high-temperature phases were also carried out.

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“…To remedy these issues, we searched for different synthetic approaches and have been inspired by recent studies aiming toward the low-temperature synthesis of various inorganic compounds, either in bulk or nanocrystalline forms, such as ammonium-thorium phosphates, 12 16 via the use of a basic medium created by the temperature-driven decomposition of urea. Herein we implemented the aforementioned approach to the synthesis of tailor-made LiFePO 4 powders via a solvothermal process in either aqueous or nonaqueous solvents.…”

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confidence: 99%

Eco-Efficient Synthesis of LiFePO[sub 4] with Different Morphologies for Li-Ion Batteries

Recham

Armand

Laffont-Dantras

et al. 2009

Electrochem. Solid-State Lett.

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LiFePO 4 is presently the most studied electrode material for battery applications. It can be prepared via solution, although it requires well-controlled pH conditions to master the iron valence state in the newly created material. Here we report its synthesis via the use of "latent bases" capable of releasing a nitrogen base upon heating. This way of controlling the reaction pH enables, in the absence of excess Li, the preparation of Fe +3 -free LiFePO 4 powders having various morphologies and showing good electrochemical performance. This approach is shown to offer great opportunities for the low-temperature synthesis of various electrode materials.Rechargeable Li-ion cells, which are powering most of today's portable electronics, are strongly considered for automotive transportation. Yet, safety and cost issues remain to be solved, prior to seeing this environmentally much-needed market extend globally. 1 The cost is mainly determined by the material abundance, thus 3d metal redox elements, such as in LiFePO 4 , 2 are receiving increased attention, while Co-or Ni-based electrodes are electronic market niches. The carbon nanopainting techniques, applied to insulating LiFePO 4 , yield high-rate yet safe batteries. 3 The environmental attractiveness of LiFePO 4 prevails over an energy density penalty due to low packing density, even more so in the presence of carbon. LiFePO 4 is the main contender for electric vehicle automakers, but natural sources of triphylite are scarce. Synthetic triphylite has to be made with directly processable grain sizes while looking for the most expeditious and energy-saving carbon coating.Precipitation from aqueous medium, under normal pressure 4 or in autoclave, 5,6 is often preferred to ceramic methods; the latter require high temperatures to ensure the diffusion of the reactants and the growth of the grains; they therefore demand high energy while leading to highly polydispersed powders. Precipitation methods in liquid media ͑e.g., solvothermal synthesis͒ 7 require little energy, and if nucleation and growth phenomena are controlled, the size distribution is much narrower.Basically, a solvothermal synthesis reaction consists in reacting metal/nonmetal-based soluble salts with a base, and increasing the temperature to promote the growth of the desired phase via Ostwald ripening. Inherent drawbacks are formation of hydroxides from the metals used, without any control over the nucleation step and possible oxidation by air oxygen. This is particularly worrisome in the case of Fe II and cobalt II .Hydrothermal synthesis of lithium iron phosphate, according to the reaction H 3 PO 4 + FeSO 4 + 3LiOH ⇒ LiFePO 4 + Li 2 SO 4 + 3H 2 O, has been demonstrated, 8 though some Fe ͑III͒ impurities remain in the final product. More recently, Delacourt et al. 4 succeeded in preparing at low temperature ͑ca. 108°C͒ electrochemically active LiFePO 4 nanoparticles having a few percent of Fe +3 9,10 via a precipitation process in a pH range close to neutrality using a waterdimethyl sulfoxide acidic mix...

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Phosphorous Acid and Urea: Valuable Sources of Phosphorus and Nitrogen in the Hydrothermal Synthesis of Ammonium-Thorium Phosphates

Cited by 21 publications

References 25 publications

Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

Phase Transformation, Vibrational and Electronic Properties of K₂Ce(PO₄)₂: A Combined Experimental and Theoretical Study

Eco-Efficient Synthesis of LiFePO[sub 4] with Different Morphologies for Li-Ion Batteries

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Phosphorous Acid and Urea: Valuable Sources of Phosphorus and Nitrogen in the Hydrothermal Synthesis of Ammonium-Thorium Phosphates

Cited by 21 publications

References 25 publications

Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

Crystallization Pathways of Cerium(IV) Phosphates Under Hydrothermal Conditions: A Search for New Phases with a Tunnel Structure

Phase Transformation, Vibrational and Electronic Properties of K2Ce(PO4)2: A Combined Experimental and Theoretical Study

Eco-Efficient Synthesis of LiFePO[sub 4] with Different Morphologies for Li-Ion Batteries

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Phase Transformation, Vibrational and Electronic Properties of K₂Ce(PO₄)₂: A Combined Experimental and Theoretical Study