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Title: Crystal structure and physical properties of quaternary clathrates Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x} and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}

Abstract

Three series of vacancy-free quaternary clathrates of type I, Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x}, and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}, have been prepared by reactions of elemental ingots in vacuum sealed quartz at 800 {sup o}C. In all cases cubic primitive symmetry (space group Pm3n, a{approx}1.1 nm) was confirmed for the clathrate phase by X-ray powder diffraction and X-ray single crystal analyses. The lattice parameters show a linear increase with increase in Ge for Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}. M atoms (Zn, Pd, Cu) preferably occupy the 6d site in random mixtures. No defects were observed for the 6d site. Site preference of Ge and Si in Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y} has been elucidated from X-ray refinement: Ge atoms linearly substitute Si in the 24k site whilst a significant deviation from linearity is observed for occupation of the 16i site. A connectivity scheme for the phase equilibria in the 'Ba{sub 8}Ge{sub 46}' corner at 800 {sup o}C has been derived and a three-dimensional isothermal section at 800 {sup o}C is presented for the Ba-Pd-Zn-Ge system. Studies of transport properties carried out for Ba{sub 8{l_brace}}Cu,Pd,Zn{r_brace}{sub x}Ge{sub 46-x} and Ba{sub 8}Zn{sub x}Si{sub y}Ge{sub 46-x-y} evidenced predominantly electrons asmore » charge carriers and the closeness of the systems to a metal-to-insulator transition, fine-tuned by substitution and mechanical processing of starting material Ba{sub 8}Ge{sub 43}. A promising figure of merit, ZT {approx}0.45 at 750 K, has been derived for Ba{sub 8}Zn{sub 7.4}Ge{sub 19.8}Si{sub 18.8}, where pricey germanium is exchanged by reasonably cheap silicon. - Graphical abstract: Quaternary phase diagram of Ba-Pd-Zn-Ge system at 800 {sup o}C.« less

Authors:
; ;  [1];  [1]; ;  [2]
  1. Institute of Physical Chemistry, University of Vienna, A-1090 Wien (Austria)
  2. Institute of Solid State Physics, Vienna University of Technology, A-1040 Wien (Austria)
Publication Date:
OSTI Identifier:
21421478
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 183; Journal Issue: 10; Other Information: DOI: 10.1016/j.jssc.2010.07.047; PII: S0022-4596(10)00330-0; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BARIUM COMPOUNDS; CHARGE CARRIERS; CLATHRATES; COPPER COMPOUNDS; GERMANIUM COMPOUNDS; LATTICE PARAMETERS; MONOCRYSTALS; PALLADIUM COMPOUNDS; PHASE DIAGRAMS; PHYSICAL PROPERTIES; SILICON COMPOUNDS; SPACE GROUPS; X-RAY DIFFRACTION; ZINC COMPOUNDS; ALKALINE EARTH METAL COMPOUNDS; COHERENT SCATTERING; CRYSTALS; DIAGRAMS; DIFFRACTION; INFORMATION; SCATTERING; SYMMETRY GROUPS; TRANSITION ELEMENT COMPOUNDS

Citation Formats

Nasir, Navida, Grytsiv, Andriy, Melnychenko-Koblyuk, Nataliya, Rogl, Peter, E-mail: peter.franz.rogl@univie.ac.a, Bednar, Ingeborg, and Bauer, Ernst. Crystal structure and physical properties of quaternary clathrates Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x} and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}. United States: N. p., 2010. Web. doi:10.1016/j.jssc.2010.07.047.
Nasir, Navida, Grytsiv, Andriy, Melnychenko-Koblyuk, Nataliya, Rogl, Peter, E-mail: peter.franz.rogl@univie.ac.a, Bednar, Ingeborg, & Bauer, Ernst. Crystal structure and physical properties of quaternary clathrates Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x} and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}. United States. doi:10.1016/j.jssc.2010.07.047.
Nasir, Navida, Grytsiv, Andriy, Melnychenko-Koblyuk, Nataliya, Rogl, Peter, E-mail: peter.franz.rogl@univie.ac.a, Bednar, Ingeborg, and Bauer, Ernst. Fri . "Crystal structure and physical properties of quaternary clathrates Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x} and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}". United States. doi:10.1016/j.jssc.2010.07.047.
@article{osti_21421478,
title = {Crystal structure and physical properties of quaternary clathrates Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x} and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}},
author = {Nasir, Navida and Grytsiv, Andriy and Melnychenko-Koblyuk, Nataliya and Rogl, Peter, E-mail: peter.franz.rogl@univie.ac.a and Bednar, Ingeborg and Bauer, Ernst},
abstractNote = {Three series of vacancy-free quaternary clathrates of type I, Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}, Ba{sub 8}(Zn,Cu){sub x}Ge{sub 46-x}, and Ba{sub 8}(Zn,Pd){sub x}Ge{sub 46-x}, have been prepared by reactions of elemental ingots in vacuum sealed quartz at 800 {sup o}C. In all cases cubic primitive symmetry (space group Pm3n, a{approx}1.1 nm) was confirmed for the clathrate phase by X-ray powder diffraction and X-ray single crystal analyses. The lattice parameters show a linear increase with increase in Ge for Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y}. M atoms (Zn, Pd, Cu) preferably occupy the 6d site in random mixtures. No defects were observed for the 6d site. Site preference of Ge and Si in Ba{sub 8}Zn{sub x}Ge{sub 46-x-y}Si{sub y} has been elucidated from X-ray refinement: Ge atoms linearly substitute Si in the 24k site whilst a significant deviation from linearity is observed for occupation of the 16i site. A connectivity scheme for the phase equilibria in the 'Ba{sub 8}Ge{sub 46}' corner at 800 {sup o}C has been derived and a three-dimensional isothermal section at 800 {sup o}C is presented for the Ba-Pd-Zn-Ge system. Studies of transport properties carried out for Ba{sub 8{l_brace}}Cu,Pd,Zn{r_brace}{sub x}Ge{sub 46-x} and Ba{sub 8}Zn{sub x}Si{sub y}Ge{sub 46-x-y} evidenced predominantly electrons as charge carriers and the closeness of the systems to a metal-to-insulator transition, fine-tuned by substitution and mechanical processing of starting material Ba{sub 8}Ge{sub 43}. A promising figure of merit, ZT {approx}0.45 at 750 K, has been derived for Ba{sub 8}Zn{sub 7.4}Ge{sub 19.8}Si{sub 18.8}, where pricey germanium is exchanged by reasonably cheap silicon. - Graphical abstract: Quaternary phase diagram of Ba-Pd-Zn-Ge system at 800 {sup o}C.},
doi = {10.1016/j.jssc.2010.07.047},
journal = {Journal of Solid State Chemistry},
number = 10,
volume = 183,
place = {United States},
year = {Fri Oct 15 00:00:00 EDT 2010},
month = {Fri Oct 15 00:00:00 EDT 2010}
}