*Synthesis and Investigation of Ceramic Materials for Medium-Temperature Solid Oxide Fuel… DOI: http://dx.doi.org/10.5772/intechopen.105108*

range and sufficiently high p-type electrical conductivity [6, 7]. Among them, the highest conductivity is observed for manganese-, cobalt-, and nickel-containing oxides. The conductivity of such perovskites can be further enhanced by increasing the concentration of charge carriers (holes) due to the heterovalent substitution of La3+ for cations of alkaline earth elements M2+ = Ca, Sr, or Ba [8]. Oxides with a perovskite structure constitute a large class of complex oxides with ABO3-type unit cells (**Figure 1**). A distinctive feature of perovskites is the possibility of cationic substitution in both A and B positions in a wide range of concentrations [9]. In practice, most crystals with a cubic perovskite structure crystallize in a lower symmetry with the distortion of the cubic structure to orthorhombic, hexagonal, or tetragonal one.

The variation of the substituting cations percentage within a fairly wide range and changing their oxidation degrees allow the simulation of functional properties of perovskite-like oxide systems.

Strontium lanthanum manganites such as La1-xSrxMnO3 (LSM) with perovskite structure are extensively used as cathodes of solid oxide fuel cells, providing the best performances in the high-temperature range (800–1000°C) [10]. For mediumtemperature fuel cells, lanthanum cobaltites and nickelates seem to be most promising, since their electrical conductivity exceeds that of lanthanum manganites due to a higher specific surface reactivity determined by a lower strength of metal-oxygen (Me–O) bond [11]. The development of processes for obtaining efficient electrolyte and cathode materials for SOFCs is an important R&D goal.

The most economically efficient approach to this problem is the use of liquid-phase synthetic methods, including co-crystallization of salts, co-precipitation of hydroxides, sol-gel, and hydrothermal. These approaches afford fine powders and nanoceramic materials-based thereon, also providing a reduced energy consumption due to the reduced temperature of powder synthesis and ceramics sintering [12].

The preparation of solid oxide electrolyte and cathode materials and their characterization to find the relationships such as "composition – synthesis technology – structure – properties" afford the determination of their optimal characteristics and synthesis conditions.

**Figure 1.** *Perovskite structure.*
