Electrical conductivity perovskites

ELECTRICAL CONDUCTIVE PEROVSKITE ANODES IN SULFUR-BASED... 

S. Sunde, K. Nisancioglu, T. Gur, Critical Analysis of Potentiostatic Step Data for Oxygen Transport in Electrically Conducting Perovskites . J. Electrochem. Soc. 143, 3497-3504 (1996)... 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

Another important group of oxide materials with a very low electrical conductivity is the oxide dielectrics. A number of these are based upon the perovskites, MXO3 or M0 X02. The archetype of these materials is BaTiC>3, which has a high dielectric constant, or relative permittivity to vacuum, the value at room temperature being 1600, and commercial use is made of the isostructural PbTi(>3 and ZrTi03 which form solid solutions, the PZT dielectrics. These materials lose their dielectric properties as the temperature... 

Oxides play many roles in modem electronic technology from insulators which can be used as capacitors, such as the perovskite BaTiOs, to the superconductors, of which the prototype was also a perovskite, Lao.sSro CutT A, where the value of x is a function of the temperature cycle and oxygen pressure which were used in the preparation of the material. Clearly the chemical difference between these two materials is that the capacitor production does not require oxygen partial pressure control as is the case in the superconductor. Intermediate between these extremes of electrical conduction are many semiconducting materials which are used as magnetic ferrites or fuel cell electrodes. The electrical properties of the semiconductors depend on the presence of transition metal ions which can be in two valence states, and the conduction mechanism involves the transfer of electrons or positive holes from one ion to another of the same species. The production problem associated with this behaviour arises from the fact that the relative concentration of each valence state depends on both the temperature and the oxygen partial pressure of the atmosphere. 

The Sr-doped praseodymium manganites and cobaltites have been studied by several groups as potential cathodes for ITSOFC. Kostogloudis et al. [116-118] systematically investigated the crystal structure, electrical conductivity, and thermal expansion properties of (Pr, Sr)Mn03, (Pr, Sr)Co03, and (Pr, Sr)(Co, Mn)03 systems. All compounds have the orthorhombic perovskite GdFe03-type structure (Pbnm... 

Zhong H-H, Zhou X-L, Liu X-Q, and Meng G-Y. Synthesis and electrical conductivity of perovskite Gd1 ICaICr03 (0Sx 0.3) by auto-ignition process. Solid State Ionics 2005 176 1057—1061. 

Temperature dependence of the electrical conductivity for perovskite-type solid solutions hydrogen. 1. StCCqYbon303 f3. 2. SrCeQ YQjO 3. SrCeQ Sc Q O From ref. [55]. 

Fig. 14. Temperature dependence of electrical conductivity for sputtered films of perovskite-type solid solutions. From ref. [73].

Certain oxides with a perovskite structure are generally applied to the cathode. For high temperature type SOFCs, doped-LaMn03 is used as the typical cathode. For low temperature SOFCs, LaSr(CoFe)03 or La(NiFe)03 are used as the cathode. Doped LaCo03 has a high electric conductivity and shows an excellent catalytic performance. However, the TEC of LaSrCo03 is larger than that of the electrolyte, and so Fe is substituted to reduce the TEC of the cathode. 

Li, X. Jeanloz, R. (1990) Laboratory studies of the electrical conductivity of silicate perovskites at high pressures and temperatures. J. Geophys. Res., 95,5067-78. 

Fig. 4.42 Electrical conductivities of modified perovskite proton conductors (adapted from...

Both elements form dioxides, M02, that have distorted rutile structures in which there are M M bonds. Re03 is an important oxide but Tc03 is not known to exist. The structure of red Re03, shown in Fig. 18-D-l, is also adopted by Cr03, W03, and others and is very similar to the perovskite structure. Re03 has metallic type electrical conductivity due to delocalization of the Re 1 electrons in a conduction band of the solid. 

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