Thorsten Gesing

Thorsten Gesing
Universität Bremen | Uni Bremen · Institute of Inorganic Chemistry and Crystallography

Heisenberg-Professor

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237
Publications
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Publications

Publications (237)
Article
Full-text available
A novel polymorph of ThB2O5, denoted as β-ThB2O5, was synthesised under high-temperature high-pressure (HT/HP) conditions. Via single crystal X-ray diffraction measurements, β-ThB2O5 was found to form a three-dimensional (3D) framework structure where thorium atoms are ten-fold oxygen coordinated forming tetra-capped trigonal prisms. The only other...
Article
Twelve cubic sodalites |Na8X2|[T1T2O4]6 (T1 = Al3+, Ga3+; T2 = Si4+, Ge4+; X = Cl−, Br−, I−) were examined using high-temperature (HT) X-ray diffraction experiments and TGA-DSC measurements. Temperature-dependent structure data was obtained by Rietveld refinements. Decomposition temperatures were determined using TGA-DSC data for all compounds. The...
Article
Pb 2 Sc 2 Si 2 O 9 and Pb 2 In 2 Si 2 O 9 , respectively, the scandium and indium containing structural analogues of the mineral kentrolite are grown by spontaneous crystallization from a PbO flux. The corresponding polycrystalline powder samples are synthesized by conventional solid-state approach. The compounds are thoroughly characterized using...
Article
Full-text available
Mullite‐type RMn2O5 (R = Y, rare‐earth element) ceramics are of ongoing research attentions because of their interesting crystal‐chemical and magnetic properties. We report nuclear and magnetic structures of NdMnTiO5 together with it's spectroscopic, thermogravimetric and magnetic properties. The polycrystalline sample is prepared by solid‐state sy...
Article
Full-text available
Mullite‐type RMn2O5 (R = Y, rare‐earth element) ceramics are of ongoing research attentions because of their interesting crystal‐chemical, physical, and thermal properties. We report a detailed structural, spectroscopic and thermal analysis of the series of mullite‐type RAlGeO5 (R = Y, Eu‐Lu) phases. Polycrystalline samples are prepared by solid‐st...
Article
Full-text available
We report a series of novel alkali rare-earth orthoborates K3RE3(BO3)4 (RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) prepared by high-temperature solid-state syntheses. Single crystals of K3Pr3(BO3)4, K3Er3(BO3)4, K3Tm3(BO3)4, K3Yb3(BO3)4 and K3Lu3(BO3)4 are obtained by spontaneous crystallization using a flux. Complementary single-cryst...
Article
The influence of the support basicity, according to the Lewis and Brønsted definition, was investigated for the CO 2 methanation over isostructural Ru catalysts.
Article
Full-text available
We report a detailed structural, spectroscopic, and thermogravimetric investigation of a new series of mixed-alkali rare-earth orthoborates KLi 2 RE(BO 3) 2 (RE = Dy, Ho, Er, Tm, Yb, and Y). Single crystals were directly prepared by a flux method as well as mechanically separated from the polycrystalline powder obtained from the conventional solid-...
Article
Synthesis, crystal structure and temperature-dependent behavior of Na 2 H 4 Ga 2 GeO 8 are reported. This novel gallogermanate crystallizes in space group I 4 1 /acd with room-temperature powder diffraction lattice parameters of a = 1298.05(1) pm and c = 870.66(1) pm. The structure consists of MO 4 ( M = Ga, Ge) tetrahedra in four-ring chains, whic...
Article
Full-text available
We have investigated the crystal structure of the synthetic analogue of the mineral iwateite using powder diffraction and Raman spectroscopy. Na2BaMn(PO4)2 crystallizes in the space group P-3m1 (No. 164) with cell parameters a = 5.37292(1) Å, and c = 7.09538(1) Å (Rwp = 5.7%, V = 177.38 Å3, Z = 1). The space group assignment is supported by the exp...
Article
The temperature-dependent structure-property relationships of the aluminosilicate perrhenate sodalite |Na 8 (ReO 4 ) 2 |[AlSiO 4 ] 6 (ReO 4 -SOD) were analysed via powder X-ray diffraction (PXRD), Raman spectroscopy and heat capacity measurements. ReO 4 -SOD shows two phase transitions in the investigated temperature range (13 K < T < 1480 K). The...
Article
(La,Nd)(Lu,Sc)O3 solid solution single crystals with liquidus temperatures of about 2170 °C were grown by the Czochralski method to provide perovskite substrates with a pseudocubic lattice parameter of 4.086 Å for epitaxial purposes. We achieved single crystals with diameters up to 17 mm and total lengths up to 50 mm. Relatively high crystalline qu...
Article
Full-text available
Single crystal and polycrystalline powder samples of a new potassium praseodymium oxoborate K2Pr2O(BO3)2 were prepared by high-temperature solid-state methods. The crystal structure obtained from single-crystal X-ray diffraction data was confirmed by powder X-ray data Rietveld refinement (P21/c, a = 1135.00(3) pm, b = 660.64(2) pm, c = 1072.03(3) p...
Article
Full-text available
Unique eleven-membered rings containing silicon, germanium, and tin were synthesized in good yields by the reactions of the corresponding 1,2-bis((2-bromothiophen-3-yl)methoxy)benzenes with (C6H5)2ECl2 where E = Sn, Ge, Si. The Sn and Ge congeners were crystallized, but the conformers that these rings crystallized in, were quite different. As confi...
Article
Full-text available
This study presents an investigation on the axial negative thermal expansion of α-PbAlBO4 and β-PbAlBO4. Polycrystalline and single-crystal samples were prepared by solid-state synthesis method, characterized by temperature- and pressure-dependent X-ray and neutron diffraction experiments. The axial negative linear compressibility (NLC) is known fo...
Article
Full-text available
Mullite-type Bi2Mn4O10 and R2Mn4O10 (R = rare earth element) compounds are isostructural and are of ongoing research attentions because of their interesting crystal structures and the associated multiferroic properties. We report three series of mullite-type (Bi1−xRx)2Mn4O10 compounds for R = Nd, Sm and Eu prepared by solid-state synthesis methods....
Article
Full-text available
The diverse and interesting properties of mullite-type PbFeBO4 have resulted in a growing number of publications, using both experimental and computational methodologies. However, several questions remain to be explored such as the role of the magnetic configuration on the intrinsic potential anharmonicity at a microscopic level, and on the elastic...
Article
Large single crystals of the double-perovskite Ba2ScNbO6 were grown from the melt for the first time. With a lattice parameter at room temperature of 4.11672(1) Å, this cubic double-perovskite has an excellent lattice match to BaSnO3, PbZr0.9Ti0.1O3, LaInO3, BiScO3, and other perovskites of contemporary interest. Differential thermal analysis showe...
Article
High-temperature thermochromic materials are poorly explored in fundamental research, let alone applied research, although these materials may be used as low-cost, intuitively usable sensing materials in an industrial environment. Yet, only few of these materials have been described systematically. We describe a series of yttrium-substituted bismut...
Preprint
Full-text available
Large single crystals of the double-perovskite Ba$_2$ScNbO$_6$ were grown from the melt for the first time. With a lattice parameter at room temperature of 4.11672(1) \r{A}, this cubic double-perovskite has an excellent lattice match to BaSnO$_3$, PbZr$_{0.9}$Ti$_{0.1}$O$_3$, LaInO$_3$, BiScO$_3$, and other perovskites of contemporary interest. Dif...
Article
We propose two new members of the mullite-type family, SnAlBO<sub>4</sub> and SnGaBO<sub>4</sub>, and carry out an in-depth study of their crystal properties using the hybrid method PW1PW. Both are isostructural to PbMBO<sub>4</sub> (M = Fe, Mn, Al, Ga), which show axial negative linear compressibility (ANLC), among other interesting features. We f...
Article
Full-text available
The low‐temperature behavior of single‐crystalline Bi2Mn4O10 is studied using dielectric impedance spectroscopy and inelastic neutron scattering. Several relaxation processes with pronounced anisotropic character can be identified in the frequency range between 1 Hz and 1 MHz for temperatures between 150 and 300 K. The dielectric as well as the mec...
Article
We report on a new synthesis route for pure Sm2O3 and Sm2O3‐Ni xerogels by modifying the well‐known epoxide addition method. The resulting xerogels are used to prove the suitability of samaria as a highly effective catalyst support and to determine the optimal Ni loading. Therefore, a set of five catalysts with Ni loadings between 4 wt% and 89 wt%...
Article
We report on average crystallite size-dependent structural, spectroscopic and thermoanalytic studies of Bi2Fe4O9 synthesized by a sol-gel method. In-situ heating X-ray diffraction revealed transformation of an X-ray amorphous precursor into a rhombohedral perovskite-type BiFeO3 followed by a second transformation into orthorhombic mullite-type Bi2F...
Article
Full-text available
Synthesis of chlorine-free, rare earth oxide aerogels from the lanthanide series was achieved using a modified epoxide-assisted sol-gel method. An ethanolic solution of the hydrated metal nitrate, propylene oxide, and ammonium carbonate was found to gel upon heating to 333 K. Critical point drying of the wet gel in CO2 yielded monolithic aerogels....
Article
Full-text available
Dealloyed nanoporous metals hold great promise in the field of heterogeneous catalysis; however their tendency to coarsen at elevated temperatures or under catalytic reaction conditions sometimes limit further applications. Here, we report on a highly stable nanoporous gold catalyst (npAu) functionalized with praseodymia-titania mixed oxides as syn...
Article
Powder samples of the intermediate phase between sodalite and cancrinite (INT) have been synthesized hydrothermally. The formation of the INT phase was proved by both PXRD and TGA analysis and its stoichiometric composition was found to be |Na 6.95(1) (CO 3 ) 0.48(2) (H 2 O) 6.18(6) |[AlSiO 4 ] 6 . The comparison of the intensity ratios of PXRD dat...
Article
The aluminosilicate iodide sodalite |Na 8 I 2 |[AlSiO 4 ] 6 was examined by temperature-dependent neutron time-of-flight powder diffraction from 5 K to 290 K and X-ray diffraction from 298 K to 1200 K. The temperature-dependent properties of the mean structure in space group P 4̅3 n were obtained by Rietveld analysis. A negative slope for the therm...
Article
We report on temperature-dependent structural and spectroscopic features of (Bi1-xFex)FeO3 perovskite for x = 0.15 and 0.25. Samples were synthesized by heating quantum crystalline precursors obtained by the polyol method. Crystal structures of each composition were obtained from in-house X-ray, synchrotron X-ray, and time-of-flight neutron powder...
Article
Full-text available
Spinel ferrites (T[M1-xFex]O[MxFe2-x]O4 with 0 ≤ x ≤ 1, where M is a bivalent metal ion and the superscripts denote tetrahedral and octahedral sites) are materials commonly used in electronics due to their outstanding magnetic properties. Thus, the effect of the degree of inversion, x, on these properties is well known. However, its effect on other...
Article
Applications of bismuth borate ceramics require understanding of the microscopic features, leading to macroscopic behaviors such as thermal expansion. We report the structural and spectroscopic features of Bi4B2O9 between 4 K and 900 K using a combination of temperature‐dependent neutron and X‐ray powder diffractions and Raman spectroscopy. Lattice...
Article
The rich crystal chemistry of mullite-type Bi2M4O9 (M=Fe, Al, Ga) offers multiple potential applications. In particular, the strong absorption of visible light shown by Bi2Fe4O9 has led to an influx of research on its photocatalytic properties. However, most of the published studies deal with the decolorization of dyes and take it as proof of its p...
Article
A comprehensive study of XO4²⁻-cancrinites with X = Mn, Cr, Se, Mo and W was carried out, focusing on the effect of incorporated anions on the framework structure. At room temperature an anisotropic unit cell expansion with increasing anion size was observed. The size of the incorporated anions has no influence on the framework angles or the channe...
Article
TbxGd1-xScO3 and TbxDy1−xScO3 solid-solution single crystals were grown by the Czochralski method to validate the practicability of solid solutions between neighboring RE scandates (REScO3). Within this material family, it is demonstrated that a fine-tuning of the pseudo-cubic lattice parameters between nearly all endmembers is now possible by adju...
Article
The photocatalytic activity of titanium dioxide (TiO2) results from its crystalline phase's anatase and rutile. In this regard, plasma electrolytic oxidation (PEO) is a promising process for producing highly porous surfaces with a high proportion of crystalline phases into the oxide layer on pure titanium. PEO-coatings were produced under different...
Article
Plasma electrolytic oxidation (PEO) is a type of high-voltage anodic oxidation process capable of producing a thick oxide layer with a wide variety of structural and chemical properties influenced by the electrolytic system. This process enables the combined adjustment of various characteristics, i.e. the morphology and chemical composition. The pr...
Article
The thermal expansion behavior of Li3AsW7O25 has been studied. Temperature-dependent development of crystal structural parameters is obtained from neutron time of flight powder diffraction data Rietveld refinement. Modeling of the lattice thermal expansion was carried out using Grüneisen first-order approximation for the zero-pressure equation of s...
Article
LiMn2O4-films were prepared by air-blast spray pyrolysis directly onto stainless steel foil substrate. The films were synthesized from various precursor solutions of dissolved nitrates and acetates with and without the addition of polyethylene glycol (PEG). Hereby X-ray diffraction experiments revealed that the phase compositions of the as-prepared...
Article
The structure of a new gallosilicate sodalite |Na6.16(1)(H2O)8|[Ga1.04(1)Si0.96(1)O4]6 described in space group P4¯3n with lattice parameter a = 885.208(7) pm is reported. For such a sodalite with a deviation from a 1:1 ratio in the framework cations a body-centred structure in space group I4¯3m could be expected. The structure shows structural str...
Article
The structural and spectroscopic features of the visible light photocatalyst Bi2WO6 have been studied. Polycrystalline (PC), nanocrystalline (NC) and quantum dot (QD) sized samples were produced using solid state reaction, hydrothermal and flame spray pyrolysis methods, respectively. While the crystal structures of PC and NC Bi2WO6 are well charact...
Article
The evolution of metric parameters of 2:1 and 3:2 mullites have been measured between 4 K and 1320 K using neutron and X-ray powder diffraction. Negative thermal expansion was observed at low temperature for the a-cell parameter and consequently for the cell-volume, which is more pronounced for 2:1 mullite than those for 3:2 mullite. Each parameter...
Article
Methanol as a green and renewable resource can be used to generate hydrogen by reforming, i.e., its catalytic oxidation with water. In combination with a fuel cell this hydrogen can be converted into electrical energy, a favorable concept, in particular for mobile applications. Its realization requires the development of novel types of structured c...
Article
Full-text available
Ni and Co containing precursor derived ceramics (ceramers) were prepared from a polysiloxane based preparation route. All catalysts were characterised by BET, XRD and TEM as well as by water and heptane adsorption and tested for CO2 methanation and Fischer–Tropsch synthesis. Different pyrolysis temperatures between 400 and 600 °C were used to get c...
Article
A highly porous surface with a high crystalline content and resultant photocatalytic activity is ensured through the process of plasma electrolytic oxidation on pure titanium. In the present study the morphology, crystallinity and photocatalytic activity of plasma electrolytic oxidized TiO2-surfaces were investigated. The surfaces were prepared in...
Article
The crystal structure and disorder phenomena of Al4B2O9, an aluminum borate from the mullite-type family, were studied using automated diffraction tomography (ADT), a recently established method for collection and analysis of electron diffraction data. Al4B2O9, prepared by sol-gel approach, crystallizes in the monoclinic space group C2/m. The ab in...
Article
The crystal structures of [C2H5NH3]4InBr7(1), [C(NH2)3]3InBr6(2), and [H3NCH2C(CH3)2CH2NH3]InBr5(3) were determined at 100(2) K: monoclinic, P21/n, a=1061.94(3), b=1186.40(4), c=2007.88(7) pm, β= 104.575(1)°, Z=4 for 1; monoclinic, C2/c, a=3128.81(12), b=878.42(3), c=2816.50(10) pm, β=92.1320(10)°, Z=16 for 2; orthorhombic, P212121, a=1250.33(5), b...
Article
Investigations of hydrothermal synthesis in the basic Na2O-Al2O3-SiO2-MnO4-H2O -system with variations of synthesis temperature and NaOH concentration were carried out. A permanganate bearing sodalite │Na7.7(1)(MnO4)1.7(2)(H2O)0.8(2)│[AlSiO4]6 could be obtained. The crystal structure and temperature-dependent behavior of this sodalite was examined...
Conference Paper
Full-text available
The pseudobinary system LaLuO3-LaScO3 was explored in hopes of discovering new perovskite-type substrates with pseudocubic lattice parameters above 4 A. A complete solid solution of the type (LaLuO3)(1-x)(LaScO3)(x) forms between the end members LaLuO3 and LaScO3, enabling large single crystals of (LaLuO3)(1-x)(LaScO3)(x) to be grown from the melt....
Article
Al-rich aluminum borates were prepared by different synthesis routes using various Al/B ratios, characterized by diffraction methods, spectroscopy and prompt gamma activation analysis. The ¹¹B NMR data show a small amount of BO4 species in all samples. The chemical analysis indicates a trend in the Al/B ratio instead of a fixed composition. Both me...
Article
Full-text available
Cobalt-based catalysts are often promoted with noble metals to improve the reducibility of the catalyst and provide a high number of metallic Co sites. The high cost of such noble metals requires new synthetic strategies enabling the use of such promoters at as low concentrations as possible. In this article, we present platinum-promoted Co–Al2O3 c...
Article
We report lattice thermal expansion of two alkali metal arsenotungstates possessing framework-type structures. Rietveld refinement analysis of the temperature-dependent neutron time-of-flight diffraction data revealed that K[AsW2O9] exhibits positive thermal expansion in the a- and c-directions, and negative thermal expansion in the b-direction. Op...
Article
Mullite-type Bi2Fe4O9 was synthesized using a polyol-mediated method. X-ray powder diffraction (XRD) revealed that the as-synthesized sample is nano-crystalline. It transformed into a rhombohedral perovskite-type BiFeO3 followed by a second transformation into mullite-type Bi2Fe4O9 during heating. Each structural feature, from as-synthesized into c...