Doped lanthanum

The result is the formation of a dense and uniform metal oxide layer in which the deposition rate is controlled by the diffusion rate of ionic species and the concentration of electronic charge carriers. This procedure is used to fabricate the thin layer of soHd electrolyte (yttria-stabilized 2irconia) and the interconnection (Mg-doped lanthanum chromite). 

The anode material in SOF(7s is a cermet (rnetal/cerarnic composite material) of 30 to 40 percent nickel in zirconia, and the cathode is lanthanum rnanganite doped with calcium oxide or strontium oxide. Both of these materials are porous and mixed ionic/electronic conductors. The bipolar separator typically is doped lanthanum chromite, but a metal can be used in cells operating below 1073 K (1472°F). The bipolar plate materials are dense and electronically conductive. 

Conceptually elegant, the SOFC nonetheless contains inherently expensive materials, such as an electrolyte made from zirconium dioxide stabilized with yttrium oxide, a strontium-doped lanthanum man-gaiiite cathode, and a nickel-doped stabilized zirconia anode. Moreover, no low-cost fabrication methods have yet been devised. 

Figure 8.15 Calculated composition versus oxygen stoichiometry curves for Lai- SrjCoCb-s. [The two experimental points are taken from data in A. N. Petrov, V. A. Cherepanov, and A. Y. Zuev, Thermodynamics, Defect Structure and Charge Transfer in Doped Lanthanum Cobaltites An Overview, J. Solid State Electrochem., 10, 517-537 (2006).]...

Cheng Z, Zha S, Aguilar L, and Liu M. Chemical, electrical, and thermal properties of strontium doped lanthanum vanadate. Solid State Ionics 2005 176 1921-1928. 

Oxygen Tracer Diffusion Coefficient (D ), Oxygen Surface Exchange Coefficient (Ar) and Oxygen Ionic Conductivity (a, in air) of Doped Lanthanum Cobalt Ferrite-Based Perovskites... 

The interconnect material is in contact with both electrodes at elevated temperatures, so chemical compatibility with other fuel cell components is important. Although, direct reaction of lanthanum chromite based materials with other components is typically not a major problem [2], reaction between calcium-doped lanthanum chromite and YSZ has been observed [20-24], but can be minimized by application of an interlayer to prevent calcium migration [25], Strontium doping, rather than calcium doping, tends to improve the resistance to reaction [26], but reaction can occur with strontium doping, especially if SrCr04 forms on the interconnect [27],... 

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

Ianculescu A, Braileanu A, Pasuk I, and Zaharescu M. Phase formation study of alkaline earth-doped lanthanum chromites. J. Therm. Anal. Calorimetry 2001 66 501-507. 

Armstrong TJ, Stevenson JW, Pederson LR, and Raney PE. Dimensional instability of doped lanthanum chromite. J. Electrochem. Soc. 1996 143 2919-2925. 

Carter JD, Appel CC, and Mogensen M. Reactions at the calcium doped lanthanum chromite-yttria stabilized zirconia interface. J. Sol. St. Chem. 1996 122 407—415. 

Mori M, Itoh H, Mori N, Abe T, Yamamoto O, Takeda Y, and Imanishi N. Reaction between alkaline earth metal doped lanthanum chromite and yttria stabilized zirconia In Badwal SPS, Bannister MJ, and Hannink RHJ. Science and Technology of Zirconia V. Lancaster, PA Technomic Publishing Co., 1993 776-785. 

Meadowcroft DB. Some properties of strontium-doped lanthanum chromite. Brit. J. Appl. Phys. 1969 D2 1225-1233. 

Sakai N, Kawada T, Yokokawa H, Dokiya M, and Iwata T. Sinterability and electrical conductivity of calcium-doped lanthanum chromites. J. Mater. Sci. 1990 25-,4531-4534. 

Yasuda I and Hikita T. Electrical conductivity and defect structure of calcium-doped lanthanum chromites. 7. Electrochem. Soc. 1993 140 1699-1704. 

Mori M, Yamamoto T, Itoh H, and Watanabe T. Compatibility of alkaline earth metal (Mg,Ca,Sr)-doped lanthanum chromites as separators in planar-type high-temperature solid oxide fuel cells. J. Mater. Sci. 1997 32 2423-2431. 

Tanasescu S, Orasanu A, Berger D, Jitaru I, and Shoonman J. Electrical conductivity and thermodynamic properties of some alkaline earth-doped lanthanum chromites. Int. J. Thermophysics 2005 26 543-557. 

Yasuda I and Hishinuma M. Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites. Solid State Ionics 1995 80 141-150. 

Bansal KP, Kumari S, Das BK, and Jain BC. Electrical conduction in titania-doped lanthanum chromite ceramics. J. Mater. Sci. 1981 16 1994—1998. 

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

Larsen PH, Hendriksen PV, and Mogensen M. Dimensional stabihty and defect chemistry of doped lanthanum chromites. J. Thermal Analysis 1997 49 1263-1275. 

Montross CS, Yokokawa H, Dokiya M, and Bekessy L. Mechanical properties of magnesia-doped lanthanum chromite versus temperature. J. Am. Ceram. Soc. 1995 78 1869-1872. 

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. 

Tai TW and Lessing PA. Modified resin-intermediate of perovskite powders. Part II. Processing for fine, nonagglomerated strontium-doped lanthanum chromite powders. J. Mater. Res. 1992 7 511-519. 

Berger D, Jitaru I, Stanica N, Perego R, and Schoonman J. Complex precursors for doped lanthanum chromite synthesis. J. Mater. Synth. Proc. 2001 9 137-142. 

Deshpande K, Mukasyan A, and Varma A. Aqueous combustion synthesis of strontium-doped lanthanum chromite ceramics. J. Am. Ceram. Soc. 2003 86 1149-1154. 

Ovenstone J, Chan KC, and Ponton B. Hydrothermal processing and characterisation of doped lanthanum chromite for use in SOFCs. J. Mater. Sci. 2002 37 3315-3322. 

Suzuki M, Sasaki H, and Kajimura A. Oxide ion conductivity of doped lanthanum chromite thin film interconnects. Solid State Ionics 1997 96 83-88. 

Paulik SW, Hardy J, Stevenson JW, and Armstrong TR. Sintering of non-stoichiomet-ric strontium doped lanthanum chromite, J. Mater. Lett. 2000 19 863-865. 

Single-phase perovskite MIECs such as Sr-doped lanthanum cobaltite (LSC), lanthanum ferrite (LSF), lanthanum cobalt ferrite (LSCF) and samarium cobaltite (SSC), and Ca-doped lanthanum ferrite (LCF) [13] are sometimes used alone in SOFC cathodes, as depicted in the lower right-hand comer of Figure 6.1, but combining an... 

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