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Electronic conduction in La-based perovskite-type oxides

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ABSTRACT

A systematic study of La-based perovskite-type oxides from the viewpoint of their electronic conduction properties was performed. LaCo0.5Ni0.5O3±δ was found to be a promising candidate as a replacement for standard metals used in oxide electrodes and wiring that are operated at temperatures up to 1173 K in air because of its high electrical conductivity and stability at high temperatures. LaCo0.5Ni0.5O3±δ exhibits a high conductivity of 1.9 × 103 S cm−1 at room temperature (R.T.) because of a high carrier concentration n of 2.2 × 1022 cm−3 and a small effective mass m∗ of 0.10 me. Notably, LaCo0.5Ni0.5O3±δ exhibits this high electrical conductivity from R.T. to 1173 K, and little change in the oxygen content occurs under these conditions. LaCo0.5Ni0.5O3±δ is the most suitable for the fabrication of oxide electrodes and wiring, though La1−xSrxCoO3±δ and La1−xSrxMnO3±δ also exhibit high electronic conductivity at R.T., with maximum electrical conductivities of 4.4 × 103 S cm−1 for La0.5Sr0.5CoO3±δ and 1.5 × 103 S cm−1 for La0.6Sr0.4MnO3±δ because oxygen release occurs in La1−xSrxCoO3±δ as elevating temperature and the electrical conductivity of La0.6Sr0.4MnO3±δ slightly decreases at temperatures above 400 K.

No MeSH data available.


XANES spectra for LaCo1−xNixO3±δ measured at AichiSR. (a) Co K-edges and (b) Ni K-edges.
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Figure 13: XANES spectra for LaCo1−xNixO3±δ measured at AichiSR. (a) Co K-edges and (b) Ni K-edges.

Mentions: In addition, the bond valence sum (BVS) for the B-site ions also exhibited an anomaly between 0.20 < x < 0.30 and sharply increased for x > 0.30. This result is of importance because the BVS should essentially decrease as the Ni2+ content increases, i.e. the Co3+ content decreases. Considering this anomaly and the ionic radius of Ni (i.e. Ni2+ > Ni3+), Ni2+ and Ni3+ are proposed to be dominant for x ≤ 0.20 and x ≥ 0.30, respectively. Figure 13 shows the x-ray absorption near edge structure (XANES) spectra for LaCo1−xNixO3±δ. The Ni K-edge was shifted to the high energy side with the increasing x, whereas the Co K-edge did not change with x, i.e. the valence of Ni changed from 2+ to 3+ with the increasing x, although the valence of Co was independent of the Co/Ni ratio. That is, the valence of Ni is changed by the itinerant carriers in LaCo1−xNixO3±δ, whereas the valence of Co is changed by the itinerant carriers in La1−xSrxCoO3±δ. The valence of Ni contributes to the electronic conduction more intensely than the valence of Co in LaCo1−xNixO3±δ.


Electronic conduction in La-based perovskite-type oxides
XANES spectra for LaCo1−xNixO3±δ measured at AichiSR. (a) Co K-edges and (b) Ni K-edges.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5036473&req=5

Figure 13: XANES spectra for LaCo1−xNixO3±δ measured at AichiSR. (a) Co K-edges and (b) Ni K-edges.
Mentions: In addition, the bond valence sum (BVS) for the B-site ions also exhibited an anomaly between 0.20 < x < 0.30 and sharply increased for x > 0.30. This result is of importance because the BVS should essentially decrease as the Ni2+ content increases, i.e. the Co3+ content decreases. Considering this anomaly and the ionic radius of Ni (i.e. Ni2+ > Ni3+), Ni2+ and Ni3+ are proposed to be dominant for x ≤ 0.20 and x ≥ 0.30, respectively. Figure 13 shows the x-ray absorption near edge structure (XANES) spectra for LaCo1−xNixO3±δ. The Ni K-edge was shifted to the high energy side with the increasing x, whereas the Co K-edge did not change with x, i.e. the valence of Ni changed from 2+ to 3+ with the increasing x, although the valence of Co was independent of the Co/Ni ratio. That is, the valence of Ni is changed by the itinerant carriers in LaCo1−xNixO3±δ, whereas the valence of Co is changed by the itinerant carriers in La1−xSrxCoO3±δ. The valence of Ni contributes to the electronic conduction more intensely than the valence of Co in LaCo1−xNixO3±δ.

View Article: PubMed Central - PubMed

ABSTRACT

A systematic study of La-based perovskite-type oxides from the viewpoint of their electronic conduction properties was performed. LaCo0.5Ni0.5O3&plusmn;&delta; was found to be a promising candidate as a replacement for standard metals used in oxide electrodes and wiring that are operated at temperatures up to 1173 K in air because of its high electrical conductivity and stability at high temperatures. LaCo0.5Ni0.5O3&plusmn;&delta; exhibits a high conductivity of 1.9 &times; 103 S cm&minus;1 at room temperature (R.T.) because of a high carrier concentration n of 2.2 &times; 1022 cm&minus;3 and a small effective mass m&lowast; of 0.10 me. Notably, LaCo0.5Ni0.5O3&plusmn;&delta; exhibits this high electrical conductivity from R.T. to 1173 K, and little change in the oxygen content occurs under these conditions. LaCo0.5Ni0.5O3&plusmn;&delta; is the most suitable for the fabrication of oxide electrodes and wiring, though La1&minus;xSrxCoO3&plusmn;&delta; and La1&minus;xSrxMnO3&plusmn;&delta; also exhibit high electronic conductivity at R.T., with maximum electrical conductivities of 4.4 &times; 103 S cm&minus;1 for La0.5Sr0.5CoO3&plusmn;&delta; and 1.5 &times; 103 S cm&minus;1 for La0.6Sr0.4MnO3&plusmn;&delta; because oxygen release occurs in La1&minus;xSrxCoO3&plusmn;&delta; as elevating temperature and the electrical conductivity of La0.6Sr0.4MnO3&plusmn;&delta; slightly decreases at temperatures above 400 K.

No MeSH data available.