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Preparation and Properties of La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ-Ce_0.8Sm_0.2O_2-δ Composite Cathode Materials

Author: JiChunYan
Tutor: XuQing
School: Wuhan University of Technology
Course: Materials Science
Keywords: CeO2 -based electrolyte materials LSCF-SDC composite cathode Coprecipitation Thermal expansion Mixed conductivity Chemical compatibility
CLC: TB331
Type: Master's thesis
Year: 2006
Downloads: 237
Quote: 1
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Abstract

La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{3 - ^δ} (LSCF) perovskite-type composite oxide has excellent electron - ion mixed conductivity properties, is the cathode candidate materials for solid oxide fuel cells (SOFC). However, its thermal expansion coefficient is higher, it is difficult to match with other SOFC element. The addition of electrolyte materials in which it is possible to improve its overall performance. In this paper, carbonate co-precipitation the prepared Ce _{0.8 0.2} O _{2 - ^δ} (M = Gd, Sm, Pr) electrolyte material, the preparation process of the material, the oxygen ion-conductive properties, and thermal expansion properties of research to selection of Ce _0.8 Sm _0.2 O _{2 - ^δ} (SDC) and LSCF composite prepared La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{3 - ^δ}-Ce _0.8 Sm _0.2 O _{2 - ^δ} (LSCF-SDC) composite cathode materials, the overall performance of LSCF-SDC composite cathode material with excellent overall performance cathode material for the research and development of experimental and theoretical basis. The this thesis carbonate coprecipitation the prepared Ce _0.8 O M _{0.2 _{2 - ^-δ} (M = Gd , Sm, Pr) powder. The results show that: the precipitating agent and the metal ion molar ratio of the precipitation reaction temperature, the aging time after the reaction, the heat treatment temperature has a significant impact on the crystal structure and morphology of the powder. Experimental study to determine the appropriate synthesis conditions, and preparation of ultrafine powders of CeO ₂-based electrolyte. AC impedance spectroscopy test Gd, Sm, Pr oxygen ion conductivity of doped CeO ₂-based electrolyte materials. Price change in Pr Ce _0.8 Pr _0.2 O _{2 - ^δ}, the introduction of the electronic conductance, makes the same test temperature, the highest conductivity of Gd _0.2 O _{2 - ^-δ} Ce ion conductor of Ce _0.8 < sub> 0.8} Sm _0.2 O _{2 - ^δ}, Ce _0.8 Sm _0.2 O _{- the ^δ} conductivity slightly higher. Glycine - Nitrate the synthesized LSCF ultrafine powder, the mass percent content by the SDC LSCF-SDC composite cathode materials prepared in the proportion of 30-60%, the thermal expansion properties of the material. The results show that: with the the SDC content of the increase, LSCF-SDC composite cathode thermal expansion of the turning point on the curve to move from pure LSCF 650 ℃ 40% La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{3 - ^δ} -60? _0.8 Sm _0.2 O _{- the ^δ} 770 ° C, the thermal expansion of the composite cathode of LSCF - SDC curve tends to become a straight line. 50% La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{3 - ^δ} -50? _0.8 Sm _0.2 O _{2 - ^δ} composite cathode at 100 to 730 ° C temperature range within the thermal expansion coefficient of 14.4 × 10 ^{-6 K ^{-1 , and matches with the doped CeO ₂-based electrolyte material. DC four-probe method and AC impedance spectroscopy study LSCF-SDC composite cathode electron - ion hybrid conductive properties. Found that the total electrical conductivity of the sample is sharply, ionic conductivity is increased slightly with increasing the content of SDC. 50% La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{3 - ^δ} -50? _0.8 Sm _0.2 O _{2 - ^δ} composite cathode at 600 to 800 ℃ temperature range within the total conductivity 100S · cm ^{-1 more to meet the SOFC cathode applications requirements. By XRD, back-scattered electron image and X-ray spectroscopy analysis test means LSCF-SDC composite cathode distribution of state of the two-phase, as well as the LSCF with the SDC the chemical compatibility. Found that two-phase composite cathode of LSCF-SDC is uniformly distributed, and the mutual diffusion phenomenon of presence of the two phases during the sintering process. After sintering at 1200 ℃ 12h 60% La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{, 3 - ^δ} -40? _0.8 Sm _0.2 O _{2 - ^{δ 50% La _0.6 Sr _0.4 Co _0.8 Fe _0.2 O _{3 - ^δ} -50? _0.8 Sm _0.2 O _{2 - ^δ} composite cathode SrCeO ₃ phase that LSCF-SDC as the long-term stability of the cathode material to be studied further.}}}}}

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Preparation and Properties of La0.6Sr0.4Co0.8Fe0.2O3-δ-Ce0.8Sm0.2O2-δ Composite Cathode Materials

Abstract

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Preparation and Properties of La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ-Ce_0.8Sm_0.2O_2-δ Composite Cathode Materials