Comparison of Electrical Conductivities in Complex Perovskites and Layered Perovskite for Cathode Materials of Intermediate Temperature-operating Solid Oxide Fuel Cell

Abstract

Electrical conductivities of complex perovskites, layered perovskite and Sr doped layered perovskite oxides were measured and analyzed for cathode materials of Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFCs). The electrical conductivities of Sm 1-x Sr x CoO 3-δ (x = 0.3 and 0.7) exhibit a metal-insulator transition (MIT) behavior as a function of temperature. However, Sm 0.5 Sr 0.5 CoO 3-δ (SSC55) shows metallic conductivity characteristics and the maximum electrical conductivity value compared to the values of Pr 0.5 Sr 0.5 CoO 3-δ (PSC55) and Nd 0.5 Sr 0.5 CoO 3-δ (NSC55). The electrical conductivity of SmBaCo 2 O 5+δ (SBCO) exhibits a MIT at about 250 o C. The maximum conductivity is 570 S/cm at 200 o C and its value is higher than 170 S/cm over the whole temperature range tested. SmBa 0.5 Sr 0.5 Co 2 O 5+δ (SBSCO), 0.5 mol% Sr and Ba substituted at the layered perovskite shows a typically metallic conductivity that is very similar to the behavior of the SSC55 cathode, and the maximum and minimum electrical conductivity in the SBSCO are 1280 S/cm at 50 o C and 280 S/cm at 900 o C.

SmBa1-xCaxCo2O5+d Layered Perovskite Cathodes for Intermediate Temperature-operating Solid Oxide Fuel Cells

“…The value of electrical conductivity in SmBa 0.5 Sr 0.5 Co 2 O 5+d (SBSCO), at about 1280 S/cm at 50°C, is better than the values of SmBaCo 2 O 5+d (SBCO, 500 S/cm) and SBCCO-0.8 (466 S/cm). However, the value of electrical conductivity in SBCCO-0.8 was 330 S/cm at 700°C, which was lower than that of SBSCO (430 S/cm) but higher than that of SBCO (270 S/cm) ( Kim et al, 2010 ; Kim, 2014 ) .…”

“…All of the compositions used in this conductivity measurement showed relatively higher electrical conductivity values from relatively lower temperature ranges (50–300°C) and a rapid decrease from 300 to 900°C, which implies that metal–insulator transition (MIT) behavior is observed in SmBa 1-x Ca x Co 2 O 5+d (x = 0.01, 0.03, 0.1, and 0.2) oxide systems ( Kim, 2014 ).…”

“…This can also result in decreases in electrical conductivity. For example, the movement of charge carriers can be limited due to oxygen vacancies, which increase rapidly in the range of 300–350°C; at the same time, the electrical conductivity decreases rapidly ( Kim, 2014 ). It can be seen in the literature results of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) of SmBa 0.5 Sr 0.5 Co 2 O 5+d (SBSCO) that weight decreases rapidly from 300 to 350°C; the same tendency was found for the electrical conductivity in this study ( Kim, 2014 ).…”

Influence of microstructure and applied current on the electrical conductivity of SmBaCo2O5+d cathode in solid oxide fuel cell

“…For example, perovskite oxide materials showing the complex perovskite structure can display a wide variation of physical and chemical characteristics depending on the degree of atomic substitution of each lattice site. By optimization of these characteristics, it is possible to improve not only physical properties but also electrochemical properties [17].…”

“…For example, when Ba is substituted into the A / -site, a crystal structure is formed according to the staking [CoO2]-[BaO]-[CoO2]-[LnO6] layers [19]. Especially in layered perovskites, this material has excellent oxygen mobility and surface kinetics due to many vacancies in the lattice structure, because of oxygen atoms are removed partially or completely in the [Ln-O6] layer [17]. The electrical conductivities displayed in Table 1 have been generally measured through experimental conditions using dense sample.…”