Constitution of the systems {V,Nb,Ta}-Sb and physical properties of di-antimonides {V,Nb,Ta}Sb-2

Fainan Failamani, Pavel Broz, Daniele Maccio, Stephan Puchegger, Helmut Müller, Leonid P. Salamakha, Herwig Michor, Andrij Grytsiv, Adriana Saccone, Ernst Bauer, Gerald Giester, Peter Franz Rogl

The binary phase diagrams {V,Nb,Ta}-Sb below 1450 °C were studied by means of XRPD, EPMA, and DTA measurements. In the V-Sb system, five stable binary phases were obsd. in this investigation: V3+xSb1-x, lT-V3Sb2, hT-V2-xSb, V7.46Sb9, V1-xSb2. The V-Sb phase diagram is characterized by two degenerate eutectic reactions: LV3+xSb1-x+(V) (T > 1450 °C at 18.1 at% Sb) and LV1-xSb2+(Sb) (T=(621 ± 5)°C at ~99 at% Sb), three peritectic reactions: L + V3+xSb1-xhT-V2-xSb (T=(1230 ± 10)°C at ~42 at% Sb), L + hT-V2-xSbV7.46Sb9 (T=(920 ± 10)°C at ~87 at% Sb), and L + V7.46Sb9V1-xSb2 (T=(869 ± 5)°C at ~88 at% Sb), a peritectoid reaction: V3+xSb1-x + hT-V2-xSblT-V3Sb2 at (875 ± 25)°C, a eutectoid reaction: hT-V2-xSblT-V3Sb2+V7.46Sb9 at (815 ± 15)°C and congruent melting of V3+xSb1-x (T > 1450 °C). An X-ray single crystal study of V5Sb4C1-x proved the existence of interstitial elements in the octahedral voids of a partially filled Ti5Te4-type structure (x~0.5; RF2 = 0.0101), therefore this phase (earlier labeled "V5Sb4") was excluded from the binary equil. phase diagram. V5Sb4C1-x is the first representative of a filled Ti5Te4-type structure. A re-investigation of the Nb-Sb system removed the contradiction between the hitherto reported phase diagrams and confirmed the version derived by Melnyk et al. (see ref. [1]). Three binary phases exist in the Ta-Sb system: Ta3+xSb1-x, Ta5Sb4, TaSb2. Due to instrumental limits (=1450 °C), only the peritectic reaction of TaSb2: L + Ta5Sb4 TaSb2 ((1080 ± 10)°C at ~92 at% Sb) and a degenerate Sb-rich eutectic reaction (LTaSb2+(Sb); (622 ± 5)°C; ~99 at% Sb) have been detd. Phys. properties (mech. and transport properties) of binary di-antimonides were investigated with respect to a potential use of these metals either as diffusion barriers or electrodes for thermoelec. devices based on skutterudites. All group-V metal di-antimonides have low metallic-type resistivity and relatively high thermal cond. Magnetic field has little influence on the resistivity of V1-xSb2 at low temp., while on {Nb,Ta}Sb2 it increases the resistivity, esp. on NbSb2. The coeff. of thermal expansion (CTE) decreases from V1-xSb2 to TaSb2, particularly the CTE value of NbSb2 is in range of av. n-type filled skutterudites. In contrast to the CTE value, elastic moduli increase from V1-xSb2 to TaSb2. The value for V1-xSb2 is in the range of Sb-based skutterudites, whereas the values for {Nb,Ta}Sb2 are significantly higher.

Institut für Physikalische Chemie, Fakultätszentrum für Nanostrukturforschung, Institut für Mineralogie und Kristallographie, Institut für Materialchemie
Externe Organisation(en)
Christian Doppler Laboratory for Thermoelectricity, Masaryk University, Università degli Studi di Genova, Technische Universität Wien
Anzahl der Seiten
ÖFOS 2012
104017 Physikalische Chemie, 104011 Materialchemie, 105113 Kristallographie, 104003 Anorganische Chemie
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