Hydrothermal synthesis, crystal structure, and vibrational and Mössbauer spectra of a new tricationic orthophosphate — KCo₃Fe(PO₄)₃

Abstract

Crystals of a new potassium cobalt(II) iron(II) triorthophosphate salt, KCo 3 Fe(PO 4 ) 3 , as well as amorphous nanoparticles of the same material have been produced by hydrothermal reactions, under supercritical water (SCW) conditions, of equivalent quantities of aq. CoCl 2 ·6H 2 O (2 mol/L) and K 4 P 2 O 7 (1 mol/L) in concd. HCl in a stainless steel batch reactor at 400-450°C and 25-32 MPa. The dark-violet crystals of the new salt have been characterized by single-crystal X-ray diffraction and IR, Raman, and Mössbauer spectroscopy. The Fe(II) in the new orthophosphate salt must derive from leaching of iron from the stainless steel walls of the reactor by concd. HCl under the SCW conditions. The salt crystallizes in the orthorhombic space group Pnnm, Z = 4, with unit cell parameters as follows: a = 9.672(1) Å, b = 16.457(2) Å, c = 6.2004(8) Å, V = 986.97 Å 3 . Microporous KCo 3 Fe(PO 4 ) 3 exhibits infinite chains of corner-sharing [PO 43-], [FeO 6 ], and [CoO 5 ] units, which form two large rhombus tunnels, occupied by K + ions, running parallel to [100] in the unit cell. The vibrational spectra have been interpreted partly on the basis of factor group effects and are in accord with the centrosymmetric structure of the material. The particle sizes of this new nanomaterial and their distribution have been determined by scanning electron micrography and laser scattering particle size distribution analysis, while the amorphous nanomaterial has also been characterized by X-ray powder diffraction and Raman spectroscopy.Résumé : Les cristaux du nouveau sel tri-orthophosphate de potassium, cobalt(II) et fer(II), KCo 3 Fe(PO 4 ) 3 , ainsi que des nano particules amorphe du même matériel, ont été produites par réactions hydrothermal dans des conditions supercritique de l'eau. Ils sont obtenus à partir d'un mélange équimolaire des solutions aqueuses CoCl 2 ·6H 2 O (2 mol/L), et K 4 P 2 O 7 (1 mol/L), en milieu acide HCl concentré dans un tube en acier inoxydable à températures 400-450°C, et à pression 25-32 MPa. Les cristaux violets foncés du nouveau sel ont été caractérisés par diffraction des rayons-X sur monocristal, et par spectroscopie IR, Raman et Mössbauer. Le Fe(II) du nouveau sel d'orthophosphate provient d'une infiltration à partir de la parois interne du réacteur en acier inoxydable, sous l'effet de l'acide HCl concentré dans les conditions supercritique de l'eau. Le sel cristallise dans le système orthorhombique de groupe d'espace Pnnm, avec Z = 4. Les paramètres cristallographiques de la maille sont : a = 9.672(1) Å, b = 16.457(2) Å, c = 6.2004(8) Å, V = 986.97 Å 3 . La structure microporeuse de KCo 3 Fe(PO 4 ) 3 se présente sous forme de chaînes formées des groupements [PO 4 3-], [CoO 5 ] et [FeO 6 ]. Ils partageant des atomes en commun, créant ainsi deux larges tunnels par maille élémentaire. Ils sont alignés le long de l'axe [100], en forme rhomboèdre, logés par des cations K + . Les spectres de vibration ont été interprétés en utilisant l'analyse du groupe facteur des groupements PO 4 3-. L'absence ...

Crystal structures of two alkaline earth (M = Ba and Sr) dimanganese(II) iron(III) tris(orthophosphates)

“…The present work deals with the synthesis and the crystal structures of two new isotypic alkaline earth manganese iron phosphates, namely, BaMn 2 Fe(PO 4 ) 3 and SrMn 2 Fe(PO 4 ) 3 . Their structures show a similarity with that of AM 4 (PO 4 ) 3 phosphates where A is a monovalent cation and M a divalent cation (Daidouh et al, 1999;Assaaoudi et al, 2006).…”

Synthesis, characterization and properties of erbium-based nanofibres and nanorods

“…UV visible spectra of the solid residues were recorded as KBr pellets on a HP8452A spectrometer, while the luminescence spectra were measured on a Fluoromax-2 spectrometer (scan start 218 nm; scan end 700 nm; increment 1 nm; excitation 208 nm; integration 0.2 s). Details of the measurements have been described elsewhere previously [18].…”

“…The lower dielectric constant in near-critical and supercritical water is the driving force in inducing supersaturation and precipitation of small particles of metal hydroxides. This approach has been already been used in the synthesis of highly crystalline metal oxides [14] and we ourselves have extended the method to the synthesis of new orthophosphate materials [15].…”

Synthesis of erbium hydroxide microflowers and nanostructures in subcritical water

“…UV-visible spectra of the solid residues were recorded using the KBr-pellet technique on a HP8452A spectrometer, while the luminescence spectra were measured on a Fluoromax-2 spectrometer (scan start 218 nm; scan end 700 nm; increment 1 nm; excitation 208 nm; integration 0.2 s). Details of the measurements have been described elsewhere previously [9].…”