Polytypic transformations of the HfCr2 Laves phase – Part II: Kinetics of the polymorphic C14 → C15 transformation

Aufrecht, J.; Leineweber, Andreas; Mittemeijer, E. J.

doi:10.1016/j.intermet.2011.05.010

Cited by 7 publications

(4 citation statements)

References 20 publications

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“…As expected, the unit cell volume increases with an increase in the radius of the rare earth metal i.e., the smallest value is noted for ScOs 2 and the largest for LaOs 2 . It is worthwhile to mention that for R Os 2 compounds one can observe polymorphic transition point (PTP), where the crystal structure changes 22 , 23 . Typically, by conventional arc melting techniques, the C15 (cubic) phase is formed with the light R 's (La-Pr) and the C14 (hexagonal) phase with the heavier R 's (Pr-Lu).…”

Section: Resultsmentioning

confidence: 99%

Superconductivity in a breathing kagome metals ROs2 (R = Sc, Y, Lu)

Górnicka,

Winiarski,

Walicka

et al. 2023

Sci Rep

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We have successfully synthesized three osmium-based hexagonal Laves compounds ROs2 (R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn2-type structure (P63/mmc, No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs2, a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs2 and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs2. ROs2 Laves phases can be viewed as a stacking of kagome nets interleaved with triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity at critical temperatures, Tc, of 5.36, 4.55, and 3.47 K for ScOs2, YOs2, and LuOs2, respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of ROs2 is intricate due to multiple interacting d orbitals of Os and R. Nonetheless, the kagome-derived bands maintain their overall shape, and the Fermi level crosses a number of bands that originate from the kagome flat bands, broadened by interlayer interaction. As a result, ROs2 can be classified as (breathing) kagome metal superconductors.

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Section: Resultsmentioning

confidence: 99%

Superconductivity in a breathing kagome metals ROs2 (R = Sc, Y, Lu)

Górnicka,

Winiarski,

Walicka

et al. 2023

Sci Rep

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“…C36 is indeed carried out by Shockley partial dislocation dipoles on adjacent lattice planes. This kind of transformation is not possible for the stable C15 phase, which evidently forms much more sluggishly [196].…”

Section: Polytypismmentioning

confidence: 99%

“…It appears that, if several polytypes occur as equilibrium phases, C15 appears to be the lowest-temperature phase and C14 is highesttemperature phase, with possibly intermediate C36 [17]. This temperature-dependent equilibrium polytypism was explored in quite some detail in the Cr-Ti [190][191][192][193][194] and Hf-Cr systems [195][196][197] dealing with transformation kinetics [192,193,196] and with the fault structure as a consequence of the transformation [190,191,195,197].…”

Section: Polytypismmentioning

confidence: 99%

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

2020

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Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

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“…As expected, the unit cell volume increases with an increase in the radius of the rare earth metal i.e., the smallest value is noted for ScOs2 and the largest for LaOs2. It is worthwhile to mention that for ROs2 compounds one can observe polymorphic transition point (PTP), where the crystal structure changes [22,23]. Typically, by conventional arc melting techniques, the C15 (cubic) phase is formed with the light R's (La-Pr) and the C14 (hexagonal) phase with the heavier R's (Pr-Lu).…”

Section: Resultsmentioning

confidence: 99%

Superconductivity in a breathing kagomé metals ROs2 (R = Sc, Y, Lu)

Górnicka,

Winiarski,

Walicka

et al. 2023

Preprint

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We have successfully synthesized three osmium-based hexagonal Laves compounds ROs2 (R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn2 – type structure (P63/mmc, No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs2, a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs2 and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs2. ROs2 Laves phases can be viewed as a stacking of kagomé nets interleaved wih triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity with Tc = 5.36, 4.55, and 3.47 K for ScOs2, YOs2, and LuOs2, respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of ROs2 is intricate due to multiple interacting d orbitals of Os and R. Nonetheless, the kagomé-derived bands maintain their overall shape, and the Fermi level is found originates from the kagomé flat bands that are broadened by interlayer interaction. As a result, ROs2 can be classified as (breathing) kagomé metal superconductors.

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Polytypic transformations of the HfCr2 Laves phase – Part II: Kinetics of the polymorphic C14 → C15 transformation

Cited by 7 publications

References 20 publications

Superconductivity in a breathing kagome metals ROs2 (R = Sc, Y, Lu)

Superconductivity in a breathing kagome metals ROs2 (R = Sc, Y, Lu)

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

Superconductivity in a breathing kagomé metals ROs2 (R = Sc, Y, Lu)

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