A5064772298- Inorganic Chemistry and Materials
- Crystal Structures and Properties
- Advanced Thermoelectric Materials and Devices
- X-ray Diffraction in Crystallography
- Rare-earth and actinide compounds
- Crystallization and Solubility Studies
- Iron-based superconductors research
- Zeolite Catalysis and Synthesis
- Magnetic and transport properties of perovskites and related materials
- Solid-state spectroscopy and crystallography
- Semiconductor materials and interfaces
- Glass properties and applications
- Silicon Nanostructures and Photoluminescence
- Inorganic Fluorides and Related Compounds
- Intermetallics and Advanced Alloy Properties
- Thermal Expansion and Ionic Conductivity
- Advanced Condensed Matter Physics
- Optical properties and cooling technologies in crystalline materials
- Physics of Superconductivity and Magnetism
- Boron and Carbon Nanomaterials Research
- Superconductivity in MgB2 and Alloys
- Synthesis and characterization of novel inorganic/organometallic compounds
- Ammonia Synthesis and Nitrogen Reduction
- Heusler alloys: electronic and magnetic properties
- Advanced ceramic materials synthesis
Max Planck Institute for Chemical Physics of Solids
2015-2025
Max Planck Society
2014-2024
Technische Universität Dresden
2014
University of South Florida
2009
University of Houston
2007
Koç University
2006
Lomonosov Moscow State University
2006
Max Planck Institute for Solid State Research
1998-2000
Recent studies increasingly highlight the potential applications of MBenes, a novel class two-dimensional (2D) materials, yet their production remains challenging. In this context, microcrystalline Mo
Single crystals of Ba(8)Au(5.3)Ge(40.7) [space group Pm(3)n (No. 223), a = 10.79891(8) Å] were prepared by Bridgman technique. The crystal structure refinement based on single-crystal X-ray diffraction data does not reveal any vacancies in the Au/Ge framework or cages. In addition to ionic bonding between Ba and anionic framework, direct interaction Au atoms was identified applying electron localizability indicator. As expected chemical-bonding picture, is diamagnet shows p-type electrical...
Engineering lattice thermal conductivity requires to control the heat carried by atomic vibration waves, phonons. The key parameter for quantifying it is phonon lifetime, limiting travelling distance, whose determination however at limits of instrumental capabilities. Here, we show achievement a direct quantitative measurement lifetimes in single crystal clathrate Ba7.81Ge40.67Au5.33, renowned its puzzling 'glass-like' conductivity. Surprisingly, transport dominated acoustic phonons with...
Abstract The binary germanides M 12 Ge 17 and 4 9 (M Na, K, Rb, Cs) the stannides Sn were identified by a combination of direct synthesis, thermogravimetric analysis, vibrational spectroscopy, X‐ray powder data single crystal structure analysis. E phases contain cluster anions [E ] 4− in ratio 1:2, forming hierarchical with at atomic positions hexagonal Laves phase MgZn 2 . Like phases, compounds are derivatives cubic Cr 3 Si but [Ge anions. analyses give strong evidence for existence...
The thermoelectric performance of EuZn2Sb2 and EuCd2Sb2 was optimized by mixed occupation the transition metal position. Samples in solid solution Eu(Zn1−xCdx)2Sb2 with CaAl2Si2-type crystal structure (space group m1) were prepared from elements for compositions x = 0, 0.1, 0.3, 0.5 1. properties investigated after densification products spark plasma sintering (SPS). samples show low electrical resistivity, high thermopower a lattice thermoconductivity. highest ZT value 1.06 at 650 K is obtained 0.1.
The synthesis and single crystal growth of clathrate-II Na(24)Si(136) is performed in one step applying the spark plasma treatment to precursor Na(4)Si(4). reported results demonstrate a new route intermetallic compounds facilitated by electric field current. SPS revealed offer significant opportunities as novel preparatory method for solid state materials.
The synthesis of clathrate-II germanium □24Ge136 in an ionic liquid was recently discovered.1 key step this process, the controlled oxidation reactive precursor phases by a protic acid, successfully applied to silicides M4Si4 (M = Na, K). Through method, clathrate-I compounds composition M8-xSi46 were obtained as crystalline products. synthetic method demonstrates mild oxidative route large class metastable intermetallic compounds.
The single phase clathrate-I Ba(8)Ge(43)square(3) (space group Ia3d (no. 230), a = 21.307(1) A) was synthesized by quenching the melt between cold steel plates. Specimens for physical property measurements were characterized microstructure analysis and X-ray diffraction on polycrystalline samples as well crystals. Transport properties including thermopower, electrical resistivity, thermal conductivity specific heat investigated in temperature range of 2-673 K. resistivity exhibits metal-like...
Single crystals of the type-I clathrate Ba8Ni3.5Ge42.1□0.4 (space group Pmn, no. 223, a = 10.798(2) Å, l 30 mm, ∅ 8 mm) were grown from melt using Bridgman technique. Their composition, determined by microprobe analysis, reveals distinctly lower Ni content than previously reported for limit (x 5.4) homogeneity range clathrate-I phase Ba8NixGe46−x. From single crystal X-ray diffraction data we introduce structure model that takes point defects (vacancies) □ in Ge network into account. It both...
The thermoelectric performance of EuCd2Sb2 and YbCd2Sb2 was improved by mixed cation occupation. composition, structure, properties YbxEu1−xCd2Sb2 (x=0, 0.5, 0.75, 1) have been investigated. Polycrystalline samples are prepared direct reaction the elements. Thermoelectric were investigated after densification materials spark plasma sintering. crystallizes in P3¯m1 space group. lattice parameters increase with europium content. These show low electrical resistivity, high Seebeck coefficient,...
The observation of intrinsic structural, electrical, and thermal properties from measurements on single-crystal specimens clathrate-II Na24Si136 is reported, revealing metallic conduction in agreement with electronic structure calculations. Low-temperature heat capacity corroborate a substantial density states at the Fermi level, reveal an Einstein-like mode that can be attributed to Na guest "rattling". large conductivity Na24Si136, compared literature data for other intermetallic...
The europium-containing clathrate-I EuxBa8–xCu16P30 was synthesized from the elements. Powder X-ray diffraction in combination with energy dispersive absorption spectroscopy (EDXS) and metallographic studies showed homogeneity range x ≤ 1.5. Determination of crystal structure confirmed presence an orthorhombic superstructure revealed that Eu atoms exclusively resided small pentagonal-dodecahedral cages. Magnetic measurements together are consistent a 4f7 (Eu2+) ground state for...
Including boron: K7B7Si39 (see structure; large spheres: K, small Si, B) is the first clathrate I compound with boron atoms. With 9.952(1) Å, borosilicide exhibits smallest lattice parameter among all intermetallic compounds. The composition in agreement Zintl rule.
Systematic crystal structure refinements from powder X-ray diffraction data as well density functional theory calculations demonstrate that the silicon clathrate II Si(cF136) exhibits a lattice contraction Na is introduced solely into Si(28) cages. When Si(20) cages, in addition, begin to be filled with Na, contrasting expansion results. The nonmonotonic structural response filling an indication of markedly dissimilar guest-framework interactions for Na@Si(20) and Na@Si(28).
Polycrystalline samples of the clathrate Ba${}_{8}$Au${}_{x}$Si${}_{46\ensuremath{-}x}$ were synthesized for 0.2 \ensuremath{\leqslant} $x$ 10. The homogeneity range type-I phase was determined to be 3.63 6.10 after annealing at 900 \ifmmode^\circ\else\textdegree\fi{}C, while a lower Au concentration ($x$ \ensuremath{\approx} 2.2) obtained by steel-quenching. Quasisingle materials 4.10 6.10. In this composition range, thermoelectric properties, including electrical resistivity, thermopower,...
The spark-plasma-sintering (SPS) technique has successfully been applied for the single-step direct synthesis of Ti2O3 from a mixture powders rutile/anatase with titanium. components react by diffusion through grain boundaries, forming several intermediate phases locally. A single-phase material titanium(III) oxide is obtained in compact bulk form after 180 min SPS treatment at 1473 K. electrical and thermal transport properties such SPS-prepared measured temperature range between 300 800 K...
Clathrate phases with crystal structures exhibiting complex disorder have been the subject of many prior studies. Here we report syntheses, and electronic structure, chemical bonding analysis a Li-substituted Ge-based clathrate phase refined formula Ba8Li5.0(1)Ge41.0, which is rare example ternary clathrate-I where alkali metal atoms substitute framework Ge atoms. Two different synthesis methods to grow single crystals new are presented, in addition classical approach towards polycrystalline...
Abstract The Zintl phase Ba 3 Si 4 has been synthesized from the elements at 1273 K as a single phase. No homogeneity range found. compound decomposes peritectically 1307(5) to BaSi 2 and melt. butterfly‐shaped 6− anion in crystal structure of (Pearson symbol tP 28, space group P / mnm , = 8.5233(3) Å, c 11.8322(6) Å) shows only slightly different Si‐Si bond lengths d (Si–Si) 2.4183(6) Å (1×) 2.4254(3) (4×). is diamagnetic with χ ≈ −50 × 10 −6 cm mol −1 . DC resistivity measurements show...
BaGe(5) constitutes a new type of intermetallic clathrate obtained by decomposition clathrate-I Ba(8)Ge(43)(3) at low temperatures. The crystal structure consists characteristic layers interconnected covalent bonds. is semiconducting Zintl phase.
The synthesis of the new binary Cs(8-x)Si(46) (shown here) completes series alkali metal silicides with a clathrate-I structure M(8-x)Si(46) (M = Na, K, Rb, Cs). In contrast lighter homologues, can be prepared only at elevated pressures. compound was obtained 1200 degrees C between 2-10 GPa and Cs content rises applied pressure.
The clathrate-I phase Ba8−xSi46 (space group Pm3̅n) was synthesized by oxidation of Ba4Li2Si6 with gaseous HCl. Microcrystalline powders the clathrate were obtained within a few minutes. reaction temperature and pressure HCl optimized to achieve good-quality crystalline products composition range 1.3 < x 1.9. new preparation route presented here provides an alternative high-pressure synthesis applied so far.
Solely on the basis of Raman spectra and quantum chemical calculations, previously unknown cluster anion Si94- (structure shown) was characterized its structure determined. The is formed as a component solid phases by thermal decomposition alkali metal monosilicides.
Abstract Sn 20.5 As 22 I 8 , a new cationic clathrate, has been prepared by using an ampoule technique. According to the X‐ray powder diffraction data, it crystallizes in face‐centered cubic space group F 23 or Fm $\bar 3$ with unit‐cell parameter of =22.1837(4) Å. Single‐crystal data allowed solution crystal structure subcell 0 =11.092(1) Å and Pm n ( R =5.7 %). (or □ 3.5 accounting for vacancies framework) possesses clathrate‐I type structure, iodine atoms occupying cages framework...
Abstract The new clathrate‐II K 8.6(4) Ge 136 has been synthesized by mild oxidation of 4 9 in the ionic liquid n ‐dodecyltrimethylammonium chloride (DTAC)/AlCl 3 at 300 °C and subsequent annealing 370 °C. Refinement crystal structure from X‐ray powder diffraction data revealed composition [space group Fd $\bar {3}$ m , a = 15.302(1) Å], which was also confirmed energy‐dispersive spectrometry (EDXS), transmission electron microscopy, scanning microscopy on bulk material. atoms preferably...