期刊
JOURNAL OF SOLID STATE CHEMISTRY
卷 182, 期 8, 页码 2191-2201出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jssc.2009.05.041
关键词
Hydrothermal synthesis; Crystal structure; Thermal behavior; IRUV/Vis and Mossbauer spectroscopies; Magnetic measurements
资金
- Ministerio de Educacion y Ciencia [MAT2007-60400/66737-C02-01]
- Gobierno Vasco [IT-177-07, GIC07/126-IT-312-07]
- Promotion of Human Resources within the National Plan of Scientific Research, Development and Innovation
- Departamento de Investigacion y Ciencia del Gobierno Vasco/Eusko Jaurlaritza
The [(MxM2.5-xIII)-M-II(H2O)(2)((HPO3)-O-III)(y)((PO4)-O-V)(2-y)F] [M = Fe (1), x = 2.08, y = 1.58; M = Co (2), x = 2.5, y = 2; Ni x = 2.5. y = 21 compounds have been synthesized using mild hydrothermal conditions at 170 degrees C during five days. Single-crystals of (I) and (2), and polycrystalline sample of (3) were obtained. These isostructural compounds crystallize in the orthorhombic system, space group Aba2, with a = 9.9598(2), b = 18.8149(4) and c = 8.5751(2)angstrom for (1), a = 9.9142(7), b = 18.570(1) and c = 8.4920(5)angstrom for (2) and a = 9.8038(2), b = 18.2453(2) and c = 8.4106(1) angstrom for (3), with Z = 8 in the three phases. An X-ray diffraction study reveals that the crystal structure is composed of a three-dimensional skeleton formed by [MO5F] and [MO4F2] (M = Fe, Co and Ni) octahedra and [HPO3] tetrahedra, partially substituted by [PO4] tetrahedra in phase (1). The IR spectra show the vibrational modes of the water molecules and those of the (HPO3)(2-) tetrahedral oxoanions. The thermal study indicates that the limit of thermal stability of these phases is 195 degrees C for (1) and 315 degrees C for (2) and (3). The electronic absorption spectroscopy shows the characteristic bands of the Fe(II), Co(II) and Ni(II) high-spin cations in slightly distorted octahedral geometry. Magnetic measurements indicate the existence of global antiferromagnetic interactions between the metallic centers with a ferromagnetic transition in the three compounds at 28, 14 and 21 K for (1), (2) and (3), respectively. Compound (1) exhibits a hysteresis loop with remnant magnetization and coercive field values of 0.72 emu/mol and 880Oe, respectively. (C) 2009 Elsevier Inc. All rights reserved.
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