Physical properties of {Ti,Zr,Hf}₂Ni₂Sn compounds

Autor(en)

V. V. Romaka, Gerda Rogl, Vilma Bursikova, Jiří Buršík, Herwig Michor, Andriy Grytsiv, E. Bauer, Gerald Giester, Peter Franz Rogl

Abstrakt

Physical properties, i.e. electrical resistivity (4.2–800 K), Seebeck coefficient (300–800 K), specific heat (2–110 K), Vickers hardness and elastic moduli (RT), have been defined for single-phase compounds with slightly nonstoichiometric compositions: Ti2.13Ni2Sn0.87, Zr2.025Ni2Sn0.975, and Hf2.055Ni2Sn0.945. From X-ray single crystal and TEM analyses, Ti2+xNi2Sn1−x, x ∼ 0.13(1), is isotypic with the U2Pt2Sn-type (space group P42/mnm, ternary ordered version of the Zr3Al2-type), also adopted by the homologous compounds with Zr and Hf. For all three polycrystalline compounds (relative densities >95%) the electrical resistivity of the samples is metallic-like with dominant scattering from static defects mainly conditioned by off-stoichiometry. Analyses of the specific heat curves Cpvs. T and Cp/T vs. T2 reveal Sommerfeld coefficients of γTi2Ni2Sn = 14.3(3) mJ mol−1 K−2, γZr2Ni2Sn = 10(1) mJ mol−1 K−2, γHf2Ni2Sn = 9.1(5) mJ mol−1 K−2 and low-temperature Debye-temperatures: θLTD = 373(7)K, 357(14)K and 318(10)K. Einstein temperatures were in the range of 130–155 K. Rather low Seebeck coefficients (<15 μV K−1), power factors (pf < 0.07 mW mK−2) and an estimated thermal conductivity of λ < 148 mW cm−1 K−1 yield thermoelectric figures of merit ZT < 0.007 at ∼800 K. Whereas for polycrystalline Zr2Ni2Sn elastic properties were determined by resonant ultrasound spectroscopy (RUS): E = 171 GPa, ν = 0.31, G = 65.5 GPa, and B = 147 GPa, the accelerated mechanical property mapping (XPM) mode was used to map the hardness and elastic moduli of T2Ni2Sn. Above 180 K, Zr2Ni2Sn reveals a quasi-linear expansion with CTE = 15.4 × 10−6 K−1. The calculated density of states is similar for all three compounds and confirms a metallic type of conductivity. The isosurface of elf shows a spherical shape for Ti/Zr/Hf atoms and indicates their ionic character, while the [Ni2Sn]n− sublattice reflects localizations around the Ni and Sn atoms with a large somewhat diffuse charge density between the closest Ni atoms.

Organisation(en)

Institut für Materialchemie, Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Masaryk University, Czech Academy of Sciences, Technische Universität Wien

Journal

Dalton Transactions

Band

51

Seiten

361-374

Anzahl der Seiten

14

ISSN

1477-9226

DOI

https://doi.org/10.1039/d1dt03198h

Publikationsdatum

2022

Peer-reviewed

Ja

ÖFOS 2012

104021 Strukturchemie, 105113 Kristallographie, 103018 Materialphysik

Schlagwörter

ASJC Scopus Sachgebiete

Inorganic Chemistry

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/103aa105-5d15-4599-ad33-462443ec09f9