Lanthanum expansion

FIGURE 4.4 Coefficients of thermal expansion of calcium- and strontium-doped lanthanum... 

Zuev A, Singheiser L, andHilpertK. Defect structure and isothermal expansion of A-site and B-site substituted lanthanum chromites. Solid State Ionics 2002 147 1-11. 

Yasuda I and Hishinuma M. Eattice expansion of acceptor-doped lanthanum chromites under high-temperature reducing atmospheres. Electrochemistry (Tokyo) 2000 68 526-530. 

Mori M and Sammes NM. Sintering and thermal expansion characterization of Al-doped and Co-doped lanthanum strontium chromites synthesized by the Pechini method. Solid State Ionics 2002 146 301-312. 

Ding X, Liu Y, Gao L, and Guo L. Effects of cation substitution on thermal expansion and electrical properties of lanthanum chromites. J. Alloys Compounds 2006 425 318-3 22. 

To introduce a barrier layer when utilizing doped ceria electrolytes (SDC, GDC, or lanthanum-doped ceria, LDC) to prevent the reduction of Ce4+ to Ce3+. Reduction of cerium cations results in unwanted electronic conductivity that lowers fuel efficiency [34], and mechanical degradation that results from the volume expansion of cerium ions upon reduction [35],... 

Cathode Porous Pt Stabilized Zr02 impregnated with praesodymium oxide and covered with SnO doped In203 Doped lanthanum manganite Extrusion, sintering 2 mm thickness 11 X 10 cm/cm°C expansion from room temperature to 1000°C 30-40% porosity... 

A numerical model to simulate the lattice expansion behavior of the doped lanthanum chromites under a cell operating condition has been proposed, and the deformation of the lanthanum chromite interconnectors has been calculated [33], In the model, the sample deformation is calculated from the profile of the oxygen vacancy concentration in the interconnector. Under a practical cell operation, the oxygen vacancy concentration in the interconnector distributes unevenly from the air side to the fuel side. The distribution of the oxygen vacancy concentration in the interconnector depends on both the temperature distribution in the interconnector and the profile of the oxygen partial pressure at the interconnector surface. Here, a numerical model calculation for the expansion behavior of the LaCrC>3 interconnector under a practical cell operation is carried out, and the uneven distribution of... 

The fabrication of the long ( 1.5 m) tubular structure starts with the cathode which is extruded ( 20 mm dia. and 2mm wall thickness) with additions to the lanthanum manganate powder of organics (e.g. starch and cellulose see Section 3.9) in order to develop the necessary porosity. The tube is sintered in air at 1500 °C. The structure must be chemically stable with respect to the subsequent processing of the electrolyte, anode and interconnect layers and have compatible thermal expansivity. It must, of course, have adequate strength to be self-supporting and also to support the electrolyte and cathode. 

Figure 1. Lanthanum laurate angle correlation of annihilation photons spectra in slowly cooled from melted state ( ) and it s expansion to narrow (NG), mean (MG) and broad (BG) Gaussians.

Electrodes The anodes of SOFC consist of Ni cermet, a composite of metallic Ni and YSZ, Ni provides the high electrical conductivity and catalytic activity, zirconia provides the mechanical, thermal, and chemical stability. In addition, it confers to the anode the same expansion coefficient of the electrolyte and renders compatible anode and electrolyte. The electrical conductivity of such anodes is predominantly electronic. Figure 14 shows the three-phase boundary at the interface porous anode YSZ and the reactions which take place. The cathode of the SOFC consists of mixed conductive oxides with perovskite crystalline structure. Sr doped lanthanum manganite is mostly used, it is a good /7-type conductor and can contain noble metals. 

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