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Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO 3

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ABSTRACT

We synthesize ScCoO3 perovskite and its solid solutions, ScCo1−xFexO3 and ScCo1−xCrxO3, under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc1−xMx)MO3 with x = 0.05–0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc0.95Co0.05)CoO3 is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc0.95Co0.05)CoO3 crystallizes in the GdFeO3-type structure similar to other members of the perovskite cobaltite family, ACoO3 (A3+ = Y and Pr-Lu). There is evidence that (Sc0.95Co0.05)CoO3 has non-magnetic low-spin Co3+ ions at the B site and paramagnetic high-spin Co3+ ions at the A site. In the iron-doped samples (Sc1−xMx)MO3 with M = (Co, Fe), Fe3+ ions have a strong preference to occupy the A site of such perovskites at small doping levels.

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Specific heat data of (Sc0.95Co0.05)CoO3 (powder was washed from KCl and then pressed into pellets at 3 GPa) at a zero magnetic field (white circles) and 90 kOe (blue diamonds) plotted as Cp/T versus T. The inset shows the details below 40 K; the red line is the fit with the equation Cp/T = γ + β1T2 between 9 and 31 K.
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Figure 5: Specific heat data of (Sc0.95Co0.05)CoO3 (powder was washed from KCl and then pressed into pellets at 3 GPa) at a zero magnetic field (white circles) and 90 kOe (blue diamonds) plotted as Cp/T versus T. The inset shows the details below 40 K; the red line is the fit with the equation Cp/T = γ + β1T2 between 9 and 31 K.

Mentions: The isothermal M versus H curves of (Sc0.95Co0.05)CoO3 and (Sc0.95M0.05)MO3 ( showed no hysteresis and passed through the origin (figure 4); no saturation behaviour was also observed at 2 K, in contrast with the expected property for free ions, that is, the Brillouin function behaviour. The M versus H curve of (Sc0.95Co0.05)CoO3 was linear at 300 K up to 70 kOe. Deviations from the Brillouin function behaviour was observed in some doped LaCoO3 samples [29]. Specific heat of (Sc0.95Co0.05)CoO3 is given on figure 5; between 9 and 31 K, the data follow the equation Cp/T = γ + β1T2 with γ = 7.86(8) mJmol−1 K−2 and β1 = 0.05452(17) mJmol−1 K−4 (the line in the inset of figure 5). Taking into account the fact that (Sc0.95Co0.05)CoO3 is an insulator, the upturn of the Cp/T values below 9 K and the apparent electronic contribution γ could originate from Schottky-type contributions or single-ion excitations. The β1 value of (Sc0.95Co0.05)CoO3 was close to that of ScRhO3 (β1 = 0.0589 mJmol−1 K−4) [28].


Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO 3
Specific heat data of (Sc0.95Co0.05)CoO3 (powder was washed from KCl and then pressed into pellets at 3 GPa) at a zero magnetic field (white circles) and 90 kOe (blue diamonds) plotted as Cp/T versus T. The inset shows the details below 40 K; the red line is the fit with the equation Cp/T = γ + β1T2 between 9 and 31 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036463&req=5

Figure 5: Specific heat data of (Sc0.95Co0.05)CoO3 (powder was washed from KCl and then pressed into pellets at 3 GPa) at a zero magnetic field (white circles) and 90 kOe (blue diamonds) plotted as Cp/T versus T. The inset shows the details below 40 K; the red line is the fit with the equation Cp/T = γ + β1T2 between 9 and 31 K.
Mentions: The isothermal M versus H curves of (Sc0.95Co0.05)CoO3 and (Sc0.95M0.05)MO3 ( showed no hysteresis and passed through the origin (figure 4); no saturation behaviour was also observed at 2 K, in contrast with the expected property for free ions, that is, the Brillouin function behaviour. The M versus H curve of (Sc0.95Co0.05)CoO3 was linear at 300 K up to 70 kOe. Deviations from the Brillouin function behaviour was observed in some doped LaCoO3 samples [29]. Specific heat of (Sc0.95Co0.05)CoO3 is given on figure 5; between 9 and 31 K, the data follow the equation Cp/T = γ + β1T2 with γ = 7.86(8) mJmol−1 K−2 and β1 = 0.05452(17) mJmol−1 K−4 (the line in the inset of figure 5). Taking into account the fact that (Sc0.95Co0.05)CoO3 is an insulator, the upturn of the Cp/T values below 9 K and the apparent electronic contribution γ could originate from Schottky-type contributions or single-ion excitations. The β1 value of (Sc0.95Co0.05)CoO3 was close to that of ScRhO3 (β1 = 0.0589 mJmol−1 K−4) [28].

View Article: PubMed Central - PubMed

ABSTRACT

We synthesize ScCoO3 perovskite and its solid solutions, ScCo1−xFexO3 and ScCo1−xCrxO3, under high pressure (6 GPa) and high temperature (1570 K) conditions. We find noticeable shifts from the stoichiometric compositions, expressed as (Sc1−xMx)MO3 with x = 0.05–0.11 and M = Co, (Co, Fe) and (Co, Cr). The crystal structure of (Sc0.95Co0.05)CoO3 is refined using synchrotron x-ray powder diffraction data: space group Pnma (No. 62), Z = 4 and lattice parameters a = 5.26766(1) Å, b = 7.14027(2) Å and c = 4.92231(1) Å. (Sc0.95Co0.05)CoO3 crystallizes in the GdFeO3-type structure similar to other members of the perovskite cobaltite family, ACoO3 (A3+ = Y and Pr-Lu). There is evidence that (Sc0.95Co0.05)CoO3 has non-magnetic low-spin Co3+ ions at the B site and paramagnetic high-spin Co3+ ions at the A site. In the iron-doped samples (Sc1−xMx)MO3 with M = (Co, Fe), Fe3+ ions have a strong preference to occupy the A site of such perovskites at small doping levels.

No MeSH data available.


Related in: MedlinePlus