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Herbert A. Wolcott

Bio: Herbert A. Wolcott is an academic researcher from Baylor University. The author has contributed to research in topics: Bond length & Lanthanide. The author has an hindex of 2, co-authored 2 publications receiving 111 citations.

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Journal ArticleDOI
TL;DR: In this paper, the lattice constants and structure for nine isotypic compounds of the hexagonal form of M(OH)3 have been determined by three-dimensional X-ray diffraction.

109 citations

Journal ArticleDOI
TL;DR: The erbium compound Er4O2(OH)8·HNO3 has been grown and the structure determined by single crystal X-ray diffraction methods.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: Ta-TMS1 as mentioned in this paper is a new member of a growing family of hexagonally packed transition-metal oxide mesoporous molecular sieves (termed TMS1) and exhibits a hexagonal array of pores which can be varied in size from 20 to 40 A and surface areas of over 500 m2/g.
Abstract: The synthesis and characterization of Ta-TMS1, a new member of a growing family of hexagonally packed transition-metal oxide mesoporous molecular sieves (termed TMS1) is described. Ta-TMS1 exhibits a hexagonal array of pores which can be varied in size from 20 to 40 A and surface areas of over 500 m2/g. The thermal and hydrothermal stabilities of Ta-TMS1 are 500 and 450 °C, respectively, making this system the most stable transition-metal oxide molecular sieve yet isolated. The high hydrocarbon adsorption capacities of this material make it a promising candidate as a catalyst support for hydrocarbon re-forming processes. The synthesis of this material was achieved by a novel approach involving the careful hydrolysis of long-chain primary amine complexes of Ta(OEt)5. This ligand-assisted templating mechanism represents a new approach to the synthesis of porous materials in that the inorganic precursor is covalently bonded to the template throughout synthesis. The high thermal stability, ease of synthesis a...

268 citations

Journal ArticleDOI
TL;DR: All phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions.
Abstract: The synthesis process and crystal structure evolution for a family of stoichiometric layered rare-earth hydroxides with general formula Ln(8)(OH)(20)Cl(4) x nH(2)O (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Y; n approximately 6-7) are described. Synthesis was accomplished through homogeneous precipitation of LnCl(3) x xH(2)O with hexamethylenetetramine to yield a single-phase product for Sm-Er and Y. Some minor coexisting phases were observed for Nd(3+) and Tm(3+), indicating a size limit for this layered series. Light lanthanides (Nd, Sm, Eu) crystallized into rectangular platelets, whereas platelets of heavy lanthanides from Gd tended to be of quasi-hexagonal morphology. Rietveld profile analysis revealed that all phases were isostructural in an orthorhombic layered structure featuring a positively charged layer, [Ln(8)(OH)(20)(H(2)O)(n)](4+), and interlayer charge-balancing Cl(-) ions. In-plane lattice parameters a and b decreased nearly linearly with a decrease in the rare-earth cation size. The interlamellar distance, c, was almost constant (approximately 8.70 A) for rare-earth elements Nd(3+), Sm(3+), and Eu(3+), but it suddenly decreased to approximately 8.45 A for Tb(3+), Dy(3+), Ho(3+), and Er(3+), which can be ascribed to two different degrees of hydration. Nd(3+) typically adopted a phase with high hydration, whereas a low-hydration phase was preferred for Tb(3+), Dy(3+), Ho(3+), Er(3+), and Tm(3+). Sm(3+), Eu(3+), and Gd(3+) samples were sensitive to humidity conditions because high- and low-hydration phases were interconvertible at a critical humidity of 10%, 20%, and 50%, respectively, as supported by both X-ray diffraction and gravimetry as a function of the relative humidity. In the phase conversion process, interlayer expansion or contraction of approximately 0.2 A also occurred as a possible consequence of absorption/desorption of H(2)O molecules. The hydration difference was also evidenced by refinement results. The number of coordinated water molecules per formula weight, n, changed from 6.6 for the high-hydration Gd sample to 6.0 for the low-hydration Gd sample. Also, the hydration number usually decreased with increasing atomic number; e.g., n = 7.4, 6.3, 7.2, and 6.6 for high-hydration Nd, Sm, Eu, and Gd, and n = 6.0, 5.8, 5.6, 5.4, and 4.9 for low-hydration Gd, Tb, Dy, Ho, and Er. The variation in the average Ln-O bond length with decreasing size of the lanthanide ions is also discussed. This family of layered lanthanide compounds highlights a novel chemistry of interplay between crystal structure stability and coordination geometry with water molecules.

223 citations

Journal ArticleDOI
Yan Yang1, Qian-Chong Zhang1, Yin-Yin Pan1, La-Sheng Long1, Lan-Sun Zheng1 
TL;DR: Investigation of two gadolinium hydroxides reveals that the thermal conductivity for 1 is significantly better than that for 2, and magnetic studies indicate that both 1 and 2 exhibit antiferromagnetic interaction.

89 citations