A Fergusonite-type phase of acceptor-doped lanthanum ortho-niobate La 1-x A x NbO 4 (A = Ca, Mg or Sr) has been synthesised by molten salt synthesis route. The high temperature behaviour and microstructure of samples doped by magnesium, calcium and strontium have been studied. The high temperature X-ray diffraction measurements in the temperature range from room temperature to 700 °C has been carried out. The scanning electron microscopy has been used to determine the samples microstructure and to compare the grain size of each material. The differences in the phase transition temperature and morphology of the samples, depending on the dopant, have been discussed.

Perovskite oxides comprise large families among the structures of oxide compounds, and several perovskite-related structures are also known. Because of their diversity in chemical composition, properties and high chemical stability, perovskite oxides are widely used for preparing solid oxide fuel cell (SOFC) components. In this work a few examples of perovskite cathode and anode materials and their necessary modifications were shortly reviewed. In particular, nickel-substituted lanthanum ferrite and iron-substituted strontium titanate as cathode materials as well as niobium-doped strontium titanate, as anode material, are described. Electrodes based on the modified perovskite oxides are very promising SOFC components.

Key words molten salt synthesis, intermediate temperature SOFC (IT-SOFC), proton conductivity.In this paper the role of the preparation route on the sintering temperature, microstructure and transport properties of BaCe 0.8 Y 0.1 Zr 0.1 O 3-δ solid solution has been studied. In particular, the samples were synthesized by means of the solid-state and molten salt synthesis method. The sample properties were investigated by means of X-ray diffraction, scanning electron microscopy and impedance spectroscopy. It was found that a good sintering of the samples could be achieved at 1500 °C for MSS preparation method. The ceramic route, even at higher temperatures, does not lead to better conductivity.

Porous CaTi 0.9 Fe 0.1 O 3-δ (CTF) perovskites were synthesized by the standard solid state method at different sintering temperatures with carbon black (CB), corn starch (CS) and potato starch (PS) as pore-forming agents. The ceramic samples of porosity between 9% and 42% with 5 -40 µm pore sizes, were obtained by a 6 h sintering at either 1130º C or 1200º C of precursor powder prepared at 1470º C. X-ray diffraction analysis proved the existence of orthorhombic single-phase perovskites crystalline structure. Electrical conductivity at 800° C was between 1.42 ×10 −2 S cm −1 and 1.86×10 −3 Scm −1 . The conductivity markedly depended on the sample porosity. It should be noted that 30% of porosity, resulted in reduction of conductivity by less than one order of magnitude. Activation energy of conductivity varied between 0.41 and 0.56 eV. Cornstarch has been chosen as the most suitable pore-forming agent for obtaining the cathode of good properties. The best amount of the cornstarch has been proposed as between 5 and 10%.

Abstract:A composite of CaTi 0 9 Fe 0 1 O 3 and electrolyte material, i.e. magnesium doped La 0 98 Mg 0 02 NbO 4 was prepared and studied. The phase content and the sample microstructure was examined by an X-ray diffraction method and scanning electron microscopy. EDS measurements were done both for composite samples and the diffusion couple. The electrical properties were studied by four terminal DC method. The hightemperature interaction between the two components of the composite has been observed. It has been suggested that lanthanum diffused into the perovskite phase and substituted for calcium whereas calcium and niobium formed the Ca 2 Nb 2 O 7 pyrochlore phase. At 1500℃ very large crystallites of the pyrochlore were observed. Regardless of strong interaction between the composite components, its total conductivity was weakly dependent on the sintering temperature. PACS