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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.

No MeSH data available.


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Portions of XRPD patterns of samples with the total composition of Sc0.9Co1−xFexO2.85 with x = 0.2, 0.4, 0.6 and 0.8. The bars show possible Bragg reflection positions for the perovskite phase and Sc2O3 impurity (from top to bottom) on a–c. A star marks a reflection from KCl in unwashed samples. On d, the bars show possible Bragg reflection positions for the perovskite phase and ScFeO3 impurity (from top to bottom).
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Figure 7: Portions of XRPD patterns of samples with the total composition of Sc0.9Co1−xFexO2.85 with x = 0.2, 0.4, 0.6 and 0.8. The bars show possible Bragg reflection positions for the perovskite phase and Sc2O3 impurity (from top to bottom) on a–c. A star marks a reflection from KCl in unwashed samples. On d, the bars show possible Bragg reflection positions for the perovskite phase and ScFeO3 impurity (from top to bottom).

Mentions: By the analogy with Sc0.9CoO2.85, we prepared solid solutions with the total composition of Sc0.9Co1−xFexO2.85 (x = 0.2, 0.4, 0.6 and 0.8). However, the samples with x = 0.2, 0.4 and 0.6 contained Sc2O3 impurity (figure 7) suggesting that the chemical composition of the perovskite phases is further shifted. Sc0.9Co0.2Fe0.8O2.85 already contained a large amount of ScFeO3 impurity with the corundum structure [32]. The lattice parameters of the solid solutions are shown on figure 8. Monotonic changes of the lattice parameters were found with a deviation for the two-phase sample with x = 0.8; this fact suggests that the solid solution limit is near x = 0.7.


Structure and cation distribution in perovskites with small cations at the A site: the case of ScCoO 3
Portions of XRPD patterns of samples with the total composition of Sc0.9Co1−xFexO2.85 with x = 0.2, 0.4, 0.6 and 0.8. The bars show possible Bragg reflection positions for the perovskite phase and Sc2O3 impurity (from top to bottom) on a–c. A star marks a reflection from KCl in unwashed samples. On d, the bars show possible Bragg reflection positions for the perovskite phase and ScFeO3 impurity (from top to bottom).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Portions of XRPD patterns of samples with the total composition of Sc0.9Co1−xFexO2.85 with x = 0.2, 0.4, 0.6 and 0.8. The bars show possible Bragg reflection positions for the perovskite phase and Sc2O3 impurity (from top to bottom) on a–c. A star marks a reflection from KCl in unwashed samples. On d, the bars show possible Bragg reflection positions for the perovskite phase and ScFeO3 impurity (from top to bottom).
Mentions: By the analogy with Sc0.9CoO2.85, we prepared solid solutions with the total composition of Sc0.9Co1−xFexO2.85 (x = 0.2, 0.4, 0.6 and 0.8). However, the samples with x = 0.2, 0.4 and 0.6 contained Sc2O3 impurity (figure 7) suggesting that the chemical composition of the perovskite phases is further shifted. Sc0.9Co0.2Fe0.8O2.85 already contained a large amount of ScFeO3 impurity with the corundum structure [32]. The lattice parameters of the solid solutions are shown on figure 8. Monotonic changes of the lattice parameters were found with a deviation for the two-phase sample with x = 0.8; this fact suggests that the solid solution limit is near x = 0.7.

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