16 research outputs found
Structural properties and thermoelectric performance of the double-filled skutterudite (Sm,Gd)y(FexNi1-x)4Sb12
No full textThe structural and thermoelectric properties of the filled skutterudite (Sm,Gd)y(FexNi1-x)4 Sb12 were investigated and critically compared to the ones in the Sm-containing system with the aim of unravelling the effect of double filling on filling fraction and thermal conductivity. Several samples (x = 0.50-0.90 and y = 0.15-0.48) were prepared by melting-sintering, and two of them were densified by spark plasma sintering in order to study their thermoelectric features. The crystallographic study enables the recognition of the role of the filler size in ruling the filling fraction and the compositional location of the p/n crossover: It has been found that the former lowers and the latter moves toward lower x values with the reduction of the filler ionic size, as a consequence of the progressively weaker interaction of the filler with the Sb12 cavity. The analysis of thermoelectric properties indicates that, despite the Sm3+/Gd3+ small mass difference, the contemporary presence of these ions in the 2a site significantly affects the thermal conductivity of both p- and n-compositions. This occurs by reducing its value with respect to the Sm-filled compound at each temperature considered, and making the overall thermoelectric performance of the system comparable to several multi-filled (Fe, Ni)-based skutterudites described in the literature
Constitution of the binary M-Sb systems (M = Ti, Zr, Hf) and physical properties of MSb2
No full textThis study is closely related to the chemical interactions in thermoelectric joints of a hot metal electrode with p- and n-type skutterudite. As a result of this work, a first and complete phase diagram has been constructed for the TiâSb system as well as partial phase diagrams (>65 at.% Sb) for the systems ZrâSb and HfâSb. Investigations are based on X-ray powder and single crystal analyses (determination of the crystal structure of Ti5Sb8with Zr2.6Ti2.4Sb8-type, space group I4122; RF= 0.032), electron probe microanalyses (EPMA) and differential thermal analyses (DTA). Physical properties were evaluated for the binary compounds MSb2(M = Ti, Zr, Hf) comprising electrical resistivity (from 4.2 K to 825 K), specific heat, thermal conductivity and thermal expansion coefficient (from 4.2 K to 300 K), Seebeck coefficient (from 300 K to 825 K) and elastic moduli at 300 K. These data will serve to evaluate the potential of MSb2compounds (M = Ti, Zr, Hf) for thermoelectric devices, where these phases predominantly appear in the diffusion zones of the hot metal electrode with p- and n-type skutterudite
Crystal Growth of Intermetallics/ Peter Gille, Yuri Grin.
No full textIn English.Intermetallic compounds are in the focus of solid-state research for a wide range of future applications, e.g. in heterogeneous catalysis, for thermoelectric generators, and basic research of quantum critical effects. A comprehensive overview is given on various crystal growth techniques that are particularly adopted to intermetallic phases. Experienced authors from leading institutes give detailed descriptions of the specific problems in crystal growth of intermetallic compounds and approaches to solve them.Grin, Yuri -- Ipser, Herbert -- Rosa, Priscila F. S. / Fisk, Zachary -- Gille, Peter -- Prokofiev, Andrey -- Schmidt, Marcus / Binnewies, Michael -- Feuerbacher, Michael -- Henkie, Zygmunt -- Ōnuki, Yoshichika / Kakihana, Masashi / Hedo, Masato / Nakama, Takao -- Mori, Takao / Vaney, Jean-Baptiste / Guélou, Gabin / Failamani, Fainan / Guo, Quansheng -- Dolinšek, Janez -- Frontmatter -- Preface -- Contents -- List of Contributing Authors -- Intermetallic compounds and their single crystals / Phase diagrams for crystal growth of intermetallics / Flux methods for growth of intermetallic single crystals / Single crystal growth of intermetallics by the Czochralski method / Floating zone growth of intermetallic compounds / Chemical vapor transport of intermetallics / Growth of high-entropy alloys / Crystal growth of the filled skutterudite arsenides by the flux method under enhanced vapor pressure / High-quality single crystal growth in heavy fermion compounds / Crystal growth of intermetallic thermoelectric materials / Electronic transport properties of complex intermetallics / Index1 online resource (292 p.
Electronic structure and optical properties of Sr2SnO4 studied with FP-LAPW method in density functional theory
No full text
Influence of nano-composites on physical and mechanical properties of high ZT-skutterudites
No full textMechanically induced combustion synthesis and thermoelectric properties of nanostructured strontium hexaboride (SrB6)
No full textThe nanoparticles of strontium hexaboride (SrB 6 ) were synthesized by a mechanically induced magnesiothermic combustion in the Mg/B 2 O 3 /SrO system. Ignition time in this system was recorded to be 23 min of milling. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM) techniques were used to characterize the combustion product. Thermal analysis was employed to assess the formation mechanism. It was revealed that Mg initially reduced B 2 O 3 in a combustive manner to generate elemental boron and a large amount of heat, resulting in the reduction of SrO by Mg at high temperature. The in-situ formed elemental Sr and B react immediately to generate SrB 6 . Thermoelectric properties of consolidated SrB 6 , including thermal conductivity, Seebeck coefficient, electrical conductivity, and figure-of-merit were evaluated at the temperature range of 300–873 K
Ferromagnetic Kondo lattice behaviour of CeZn(Zn0.29Si0.71)2
No full textWe report on the ferromagnetic Kondo lattice behavior of novel CeZn(Zn
0.29Si0.71)2, which was studied by means of ac and dc magnetic susceptibility, specific heat and resistivity measurements on flux-‐
grown single crystals as well as on sintered bulk samples. The orthorhombic CeNiSi2-‐type phase CeZn(Zn0.29Si0.71)2 [space group Cmcm, a=0.42079(1), b=1.765218(3), c=0.41619(1) nm] was identified in the course of an investigation of the phase equilibria in the Ce-‐Zn
-‐Si system (<33.3 at.% Ce) in Ref. [1]. Field dependent isothermal well as temperature dependent magnetisation measurements reveal ferromagnetic ordering of CeZn(Zn0.29Si0.71)2 below about Tc=4.4 K with a magnetically ordered moment near 1 μB/Ce at 1.9 K and 6 T. The corresponding specific heat anomaly at 4.4 K displays a significantly reduced magnitude as compared to the value expected from a basic local moment mean-‐field approach and is analysed in terms of a simple model for a ferromagnetic Kondo lattice system based on the resonant level model by Schotte and Schotte [2], thus, yielding parameters for the ferromagnetic exchange coupling J=14.6 K and the Kondo temperature TK=5 K. The effective paramagnetic moment of Ce, μeff = 2.5 μB, obtained from a Curie--. Weiss fit suggest that the
ground state of Ce-‐ions in this compound is close to 3+
On the Half-Heusler compounds Nb1-x{Ti,Zr,Hf}xFeSb: Phase relations, thermoelectric properties at low and high temperature, and mechanical properties
No full textA re-investigation of phase equilibria, crystal structure and homogeneity region of the Half-Heusler (HH)
phase in the ternary system Nb-Fe-Sb at 600 C has solved controversies in the literature confirming the
version of Melnyk et al. ([1] J. Phase Equilibria 20 (2) (1999) 113e118). For the first time transport
properties of Half-Heusler (HH) compounds NbFeSb and Nb0.85M0.15FeSb (M ¼ Ti, Zr, Hf) were studied in
the full temperature range from 4.2 to 823 K. The semiconducting material NbFeSb has an electronic
structure close to a metal-to-insulator transition, which leads to changes of the conductivity type with
the composition as well as with increasing temperature. Ti, Zr and Hf doped NbFeSb alloys show metallic
behavior and were confirmed to be high ZT p-type thermoelectric materials. Surprisingly, the lattice
thermal conductivity for the Zr-doped composition was found to be higher than those of the Ti- and Hf
doped materials; this effect can be explained in terms of mass and strain field fluctuations.
For the first time we report experimental information on thermal expansion coefficients, specific heat
and elastic moduli for these p-type compounds. The mechanical properties show a good compatibility
with those previously reported for n-type HH alloys
