Chemical synthesis of α-cobalt hydroxide

Rajamathi, Michael; Kamath, P. Vishnu; Seshadri, Ram

doi:10.1016/s0025-5408(00)00199-9

Cited by 107 publications

(93 citation statements)

References 14 publications

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“…This pre-edge feature results from a lack of inversion symmetry in crystal sites due to the presence of tetrahedral coordination of some of the cobalt ions present in the material, supporting the above conclusions. Methods used previously to make a-Co(OH) 2 materials involved electrochemical, 15 chemical, 19,26 and sonication assisted synthesis routes, 13,14 but direct electronic measurements previously could not be carried out on the resulting materials because of the low quality powder morphology, low crystallinity and the absence of suitable thin films. Few publications report the growth of Co(OH) 2 thin films on substrates.…”

Section: 27mentioning

confidence: 99%

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

et al. 2006

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) and Mn 3 (PO 4 ) 2 ?7H 2 O thin films have been prepared using a kinetically controlled vapor-diffusion method. Vectorial control by diffusion of ammonia as a base catalyst into an aqueous metal salt solution yields large area (2 cm 2 ) metal hydroxide and metal phosphate films with unique structures. No supporting substrate for growth of the films is necessary in this approach. The films were characterized using X-ray powder diffraction and scanning electron microscopy. The cobalt containing films were studied in more detail using transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption near edge structure and various chemical analysis techniques. For the first time the electronic properties and crystal structure of these materials could be studied in thin films not influenced by the presence of an underlying substrate. For Co 5 (OH) 8 (NO 3 ) 2 ?2H 2 O films, which crystallize in a layered hydrotalcite-like structure that is homogeneous from the nanoscale to the macroscale, unprecedented photoconductivity properties were observed. Resistivity measurements show that this material is a p-type semiconductor with an unusually long minority carrier lifetime and high carrier density.

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Section: 27mentioning

confidence: 99%

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

et al. 2006

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“…The resulting compound has x ¼ 0:22 which is much less than the typical values (0.5-1.0) seen in basic salts. This hydroxyl-rich composition is associated with the a-hydroxides [32,33]. The a-hydroxides are obtained by the protonation of a fraction, x, of the hydroxyl ions.…”

Section: Article In Pressmentioning

confidence: 99%

Anion mediated polytype selectivity among the basic salts of Co(II)

Ramesh

Rajamathi²,

Kamath

2006

Journal of Solid State Chemistry

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Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2 , with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and a-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 4 2À ions.

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“…A prime example of this structure is a-Co(OH) 2 , which can include a number of different counteranions. [6,7] Studies of cobalt hydroxide chloride have shown that the cobalt ions take on both octahedral and tetrahedral coordination geometries, [8] as portrayed in Figure 1c, and that changing the precursor hydrolysis rate in the synthesis process comprising hydrolysis and polycondensation varies the ratio of the different coordination arrangements, altering the structure within the layers. [9] Despite the many previous studies on the cobalt hydroxide chloride family, a detailed picture of the arrangement of metal sites, in terms of their coordination and distribution, has remained elusive.…”

Section: Introductionmentioning

confidence: 99%

Cobalt Coordination and Clustering in α‐Co(OH)₂ Revealed by Synchrotron X‐ray Total Scattering

Neilson

Kurzman

Seshadri

et al. 2010

Chemistry A European J

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Structures of layered metal hydroxides are not well described by traditional crystallography. Total scattering from a synthesis-controlled subset of these materials, as described here, reveals that different cobalt coordination polyhedra cluster within each layer on short length scales, offering new insights and approaches for understanding the properties of these and related layered materials. Structures related to that of brucite [Mg(OH)(2)] are ubiquitous in the mineral world and offer a variety of useful functions ranging from catalysis and ion-exchange to sequestration and energy transduction, including applications in batteries. However, it has been difficult to resolve the atomic structure of these layered compounds because interlayer disorder disrupts the long-range periodicity necessary for diffraction-based structure determination. For this reason, traditional unit-cell-based descriptions have remained inaccurate. Here we apply, for the first time to such layered hydroxides, synchrotron X-ray total scattering methods-analyzing both the Bragg and diffuse components-to resolve the intralayer structure of three different alpha-cobalt hydroxides, revealing the nature and distribution of metal site coordination. The different compounds with incorporated chloride ions have been prepared with kinetic control of hydrolysis to yield different ratios of octahedrally and tetrahedrally coordinated cobalt ions within the layers, as confirmed by total scattering. Real-space analyses indicate local clustering of polyhedra within the layers, manifested in the weighted average of different ordered phases with fixed fractions of tetrahedrally coordinated cobalt sites. These results, hidden from an averaged unit-cell description, reveal new structural characteristics that are essential to understanding the origin of fundamental material properties such as color, anion exchange capacity, and magnetic behavior. Our results also provide further insights into the detailed mechanisms of aqueous hydrolysis chemistry of hydrated metal salts. We emphasize the power of the methods used here for establishing structure-property correlations in functional materials with related layered structures.

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Chemical synthesis of α-cobalt hydroxide

Cited by 107 publications

References 14 publications

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

Anion mediated polytype selectivity among the basic salts of Co(II)

Cobalt Coordination and Clustering in α‐Co(OH)₂ Revealed by Synchrotron X‐ray Total Scattering

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Chemical synthesis of α-cobalt hydroxide

Cited by 107 publications

References 14 publications

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

Kinetically controlled vapor-diffusion synthesis of novel nanostructured metal hydroxide and phosphate films using no organic reagents

Anion mediated polytype selectivity among the basic salts of Co(II)

Cobalt Coordination and Clustering in α‐Co(OH)2 Revealed by Synchrotron X‐ray Total Scattering

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Cobalt Coordination and Clustering in α‐Co(OH)₂ Revealed by Synchrotron X‐ray Total Scattering