Limits...
Electronic conduction in La-based perovskite-type oxides

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±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.


Lattice parameters of La1−xAExCoO3 based on a rhombohedral unit cell: (a) lattice angle, (b) lattice length, (c) Co−O−Co bond angle and (d) Co−O bond length. Reproduced from [6] by permission of The Royal Society of Chemistry. Figure 1(e) XRD pattern for La0.6Sr0.4CoO3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC5036473&req=5

Figure 1: Lattice parameters of La1−xAExCoO3 based on a rhombohedral unit cell: (a) lattice angle, (b) lattice length, (c) Co−O−Co bond angle and (d) Co−O bond length. Reproduced from [6] by permission of The Royal Society of Chemistry. Figure 1(e) XRD pattern for La0.6Sr0.4CoO3.

Mentions: The perovskite-type structure of the doped LaCoO3 systems was confirmed via powder x-ray diffraction (XRD) analysis. The lattice parameters of La1−xAExCoO3 and XRD pattern of La0.6Sr0.4CoO3 are shown in figure 1. Powder XRD patterns were measured with CuKa radiation at R.T. (RIGAKU, RINT TTR-III, 20 ≤ 2θ ≤ 120, step scan 0.02, 50 kV–300 mA). The lattice parameters were refined by means of Rietveld analysis using the RIETAN2000 code with the powder XRD patterns. The result of the Rietveld analysis for La0.6Sr0.4CoO3 (Rwp = 10.63%, Rp = 7.51%, S = 1.43) is shown in figure 1(e) as an example. The XRD patterns were shifted systematically with the average ionic radius at the A-site (i.e. the ionic radius of the AE element and the AE concentration). However, the patterns for La1−xCaxCoO3±δ became anomalous with the increasing Ca content (x ≥ 0.25). The values for the lattice length (a), the lattice angle (α), the Co–O–Co bond angle and the Co–O bond length of each of the doped LaCoO3 systems refined via Rietveld analysis using the rhombohedral R-3c space group are shown in figures 1(a) and (b) [28–31]. The different behaviors of a and α as a function of the AE concentration for Sr, Ba and Ca are reflected in the XRD patterns. The a and α values for Sr and Ba varied depending on the AE concentration and the ionic radius of the AE element, while there was an anomaly at approximately x = 0.25 for Ca. In addition, the Co–O–Co bond angle approached 180° when the average ionic radius at the A-site increased, as shown in figure 1(c). This result indicated that the conduction path, or the connection between the CoO6 octahedra, approached 180° when the average ionic radius at the A-site increased. In contrast, the Co–O bond length did not vary with the AE element, as shown in figure 1(d). Only the Co–O bond length for Sr decreased as a function of the AE concentration for the condition wherein x ≥ 0.25. Note that the values for the Co–O bond length and Co–O–Co bond angle in La1−xSrxCoO3±δ determined in the present study are not consistent with previous reports [32, 33] because of the difference in the oxygen content and the alteration of the CoO6 octahedra, which are a direct result of the synthetic method and the reaction conditions employed.


Electronic conduction in La-based perovskite-type oxides
Lattice parameters of La1−xAExCoO3 based on a rhombohedral unit cell: (a) lattice angle, (b) lattice length, (c) Co−O−Co bond angle and (d) Co−O bond length. Reproduced from [6] by permission of The Royal Society of Chemistry. Figure 1(e) XRD pattern for La0.6Sr0.4CoO3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036473&req=5

Figure 1: Lattice parameters of La1−xAExCoO3 based on a rhombohedral unit cell: (a) lattice angle, (b) lattice length, (c) Co−O−Co bond angle and (d) Co−O bond length. Reproduced from [6] by permission of The Royal Society of Chemistry. Figure 1(e) XRD pattern for La0.6Sr0.4CoO3.
Mentions: The perovskite-type structure of the doped LaCoO3 systems was confirmed via powder x-ray diffraction (XRD) analysis. The lattice parameters of La1−xAExCoO3 and XRD pattern of La0.6Sr0.4CoO3 are shown in figure 1. Powder XRD patterns were measured with CuKa radiation at R.T. (RIGAKU, RINT TTR-III, 20 ≤ 2θ ≤ 120, step scan 0.02, 50 kV–300 mA). The lattice parameters were refined by means of Rietveld analysis using the RIETAN2000 code with the powder XRD patterns. The result of the Rietveld analysis for La0.6Sr0.4CoO3 (Rwp = 10.63%, Rp = 7.51%, S = 1.43) is shown in figure 1(e) as an example. The XRD patterns were shifted systematically with the average ionic radius at the A-site (i.e. the ionic radius of the AE element and the AE concentration). However, the patterns for La1−xCaxCoO3±δ became anomalous with the increasing Ca content (x ≥ 0.25). The values for the lattice length (a), the lattice angle (α), the Co–O–Co bond angle and the Co–O bond length of each of the doped LaCoO3 systems refined via Rietveld analysis using the rhombohedral R-3c space group are shown in figures 1(a) and (b) [28–31]. The different behaviors of a and α as a function of the AE concentration for Sr, Ba and Ca are reflected in the XRD patterns. The a and α values for Sr and Ba varied depending on the AE concentration and the ionic radius of the AE element, while there was an anomaly at approximately x = 0.25 for Ca. In addition, the Co–O–Co bond angle approached 180° when the average ionic radius at the A-site increased, as shown in figure 1(c). This result indicated that the conduction path, or the connection between the CoO6 octahedra, approached 180° when the average ionic radius at the A-site increased. In contrast, the Co–O bond length did not vary with the AE element, as shown in figure 1(d). Only the Co–O bond length for Sr decreased as a function of the AE concentration for the condition wherein x ≥ 0.25. Note that the values for the Co–O bond length and Co–O–Co bond angle in La1−xSrxCoO3±δ determined in the present study are not consistent with previous reports [32, 33] because of the difference in the oxygen content and the alteration of the CoO6 octahedra, which are a direct result of the synthetic method and the reaction conditions employed.

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±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.