Mild hydrothermal synthesis, crystal structure, thermal behavior, spectroscopic and magnetic properties of the (NH{sub 4})[Fe(AsO{sub 4}){sub 1-x}(PO{sub 4}){sub x}F] (x=0.3, 0.6, 0.8) series. Thermal transformation of (NH{sub 4})[Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}F] into the textural porous orthorhombic Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}

Journal Article · Wed Apr 15 00:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.01.026· OSTI ID:21370359

Berrocal, Teresa ^[1]; Pizarro, Jose L; Bazan, Begona ^[1]; Lezama, Luis ^[2]; Arriortua, Maria I ^[1]; Rojo, Teofilo ^[2]

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1. Departamento de Mineralogia y Petrologia, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo, 644, E-48080 Bilbao (Spain)
2. Departamento de Quimica Inorganica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco/EHU, Apdo, 644, E-48080 Bilbao (Spain)

The (NH{sub 4})[Fe(AsO{sub 4}){sub 1-x}(PO{sub 4}){sub x}F] (x=0.3, 0.6, 0.8) series of compounds has been synthesized under mild hydrothermal conditions. The compounds crystallize in the orthorhombic Pna2{sub 1} space group, with the unit-cell parameters a=13.1718(1), b=6.5966(6), c=10.797(1) A for x=0.3; a=13.081(1), b=6.5341(6), c=10.713(1) A for x=0.6 and a=13.0329(9), b=6.4994(4), c=10.6702(6) A for x=0.8, with the volumes 938.6(1), 915.7(1) and 903.8(1) A{sup 3}, respectively, with Z=8. Single crystals of (NH{sub 4})[Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}F] heated under air atmosphere at 465 deg. C remain as single crystals, changing the composition to Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}. This later phase belongs to the orthorhombic Imam space group, with the unit cell parameters a=13.328(2), b=6.5114(5), c=10.703(1) A, V=928.9(2) A{sup 3} and Z=12. The crystal structure of the ammonium phases consists of a KTP three-dimensional framework constructed by chains formed by alternating Fe(2)O{sub 4}F{sub 2} or Fe(1)O{sub 4}F{sub 2} octahedra and As/P(2)O{sub 4} or As/P(1)O{sub 4} tetrahedra, respectively. These octahedra and tetrahedra are linked by a common oxygen vertex. The chains run along the 'a' and 'b' crystallographic axes. The crystal structure of Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3} is a three-dimensional skeleton derived from that of the precursor, formed from (100) sheets stacked along the [001] direction, and interconnected by chains of alternating Fe(2)O{sub 6} octahedra and As/P(2)O{sub 4} tetrahedra sharing a vertex in the 'a' direction. Transmission electronic microscopy of this compound indicates the existence of unconnected external cavities with a BET surface area of 3.91(3) m{sup 2} g{sup -1}. The diffuse reflectance spectra in the visible region show the forbidden electronic transitions characteristic of the Fe(III) d{sup 5}-high spin cation in slightly distorted octahedral geometry, for all the compounds. The ESR spectra for all the compounds, carried out from room temperature to 4.2 K, remain isotropic with variation in temperature; the g-value is 1.99(1). Magnetic measurements indicate the predominance of antiferromagnetic interactions, with Neel temperatures near to 70.0 and 50.0 K for the ammonium phases and Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.30}, respectively. At low temperatures a spin canting phenomenon for Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.30} is detected. - Graphical abstract: The relationship between the |100| and |010| chains in (NH{sub 4})[Fe(AsO{sub 4}){sub 1-x}(PO{sub 4}){sub x}F] left and the |100| chains and the (001) sheets in Fe(AsO{sub 4}){sub 0.7}(PO{sub 4}){sub 0.3}.

• OSTI ID: 21370359
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 4; Other Information: DOI: 10.1016/j.jssc.2009.01.026; PII: S0022-4596(09)00026-7; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMMONIUM COMPOUNDS
ANTIFERROMAGNETISM
ARSENATES
ELECTRON SPIN RESONANCE
G VALUE
HYDROTHERMAL SYNTHESIS
IRON COMPOUNDS
MAGNETIC PROPERTIES
MONOCRYSTALS
NEEL TEMPERATURE
ORTHORHOMBIC LATTICES
PHOSPHATES
POROUS MATERIALS
SPACE GROUPS
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TRANSMISSION ELECTRON MICROSCOPY
ARSENIC COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
ELECTRON MICROSCOPY
MAGNETIC RESONANCE
MAGNETISM
MATERIALS
MICROSCOPY
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
RESONANCE
SYMMETRY GROUPS
SYNTHESIS
TEMPERATURE RANGE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE