Synthesis of LaSrXMg-Oxide with X=Ga, Fe, or Cr
- PDF / 132,048 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 19 Downloads / 151 Views
FF4.12.1
Synthesis of LaSrXMg-Oxide with X=Ga, Fe, or Cr Cinar Oncel and Mehmet A. Gulgun, Sabanci University, FENS, Orhanli Tuzla, Istanbul 34956 Turkiye ABSTRACT Strontium and magnesium doped lanthanum gallate (LSGM) is a promising electrolyte material for intermediate temperature range (650-800°C) solid oxide fuel cell (SOFC) applications. Formation of unwanted phases and Ga loss at high temperatures (1100-1500°C) during synthesis and under low oxygen partial pressures during operation are major hurdles that stand in LSGM’s way of full utilization. Using a polymeric precursor synthesis method, the feasibility of producing SOFC electrolyte material LSGM is investigated. The method involves complexing each constituent metal ion by the carboxyl and/or hydroxyl group of the citric acid and/or polyvinyl alcohol (PVA) in aqueous solution. The facility of this method compared with the traditional solid state reaction method was shown by synthesis of single phase and pure LSXM (X= Fe, Cr) oxides at reasonable temperatures (800°C). The X-ray diffraction patterns of LSFM and LSCM are also reported here for the first time. INTRODUCTION Lanthanum strontium gallium magnesium oxide (La0.8Sr0.2Ga0.8Mg0.2O3-δ), is one of the most promising electrolyte materials for solid oxide fuel cell (SOFC) applications [1,2]. In lanthanum gallate (LaGaO3) structure, Sr-atoms substitute for the La sites and Mg-atoms substitute for the Ga sites. Doping elements introduce oxygen vacancies and thereby increase the oxygen diffusivities through the material at intermediate temperatures [3]. LSGM exhibits oxygen ion diffusivities at intermediate temperature range (650-850°C) that are comparable to the one from ZrO2 electrolyte at 1000°C [2]. Several hurdles have to be overcome before the electrolyte will be suitable for the fuel cell applications. There are stringent requirements for SOFC electrolyte materials. Besides being a good oxygen ion conductor, the candidate oxide should maintain its stoichiometry, phase character, and crystal structure at the operating temperatures for an extended period of time. The electrolyte must be chemically inert and should have a compatible thermal expansion coefficient with the electrode materials up to the operating temperatures. Traditional production method for multi-cation oxide materials is the solid state reaction technique. In this method repetitive ball-milling and grinding steps are time consuming, and energy intensive. Besides, calcination and sintering with long holding times at high temperatures are costly [4-7]. As one of the alternative methods to produce multi-cation oxide material, the so-called urea method was suggested. The problem with this technique is the high temperatures (1400-1500°C) and long holding times required to obtain a single phase and pure mixed-oxide [8,9]. For another alternative route (citrate synthesis), the problem is the formation of second phases, which influence the stability, reactivity and ionic conductivity of the electrolyte material [10]. One of the major problems wi
Data Loading...
