Studies of the Average Valence State of the Transition Metals and the Electrical Properties of LaSr₃Fe_3-xMn_xO_10-δ (x=0.0-0.8) Mixed Conductors

Abstract:

LaSr₃Fe_3-xMn_xO_10-δ (x=0.0-0.8) mixed conductors with layered perovskite structure were prepared via citric acid method. XRD analysis showed that the cell volume decreased with Mn content. The fraction of Fe⁴⁺ concentration to the concentration of tetravalent ions decreased with the increase of Mn content. The decrease of average valence state (V_B) of transition metals of LaSr₃Fe_3-xMn_xO_10-δ samples with the increase of temperature gave rise to the drop of p type charge carriers and the increase of oxygen vacancies. According to the relationship between V_B and the numbers of the configurations of transition metals in LaSr₃Fe_3-xMn_xO_10-δ , the possible filling states of 3d orbitals of Fe and Mn ions at 700 °C and 800 °C were given. The variations of conductivities of LaSr₃Fe_3-xMn_xO_10-δ samples were interpreted on the basis of the variation of V_B and δ with temperature and Mn content, respectively. Scanning Kelvin probe measurement results revealed that the surface potential of x=0.6 sample was the highest while x=0.8 sample was the lowest. The higher the surface potential, the higher the energy needed for an electron to be released from the sample.

• Periodical: Materials Science Forum (Volume 852)
• Pages: 95-100
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.852.95
• Online since: April 2016
• Authors: Qin Li, Wei Bin Wan, Shuai Li, Zhi Bing Sheng, Guo Guang Zhang
• Keywords: Average Valence State, Oxygen Nonstoichiometry, Seebeck Coefficient, Surface Potential

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