KOLOID DEPOSITION Sm0,2Ce0,8O2-? THAT IS SYNTHESIS WITH SOLID PHASE REACTION METHOD AND COOPRESSIPITATION IN SUBSTRATE La0,8Sr0,2MnO3-Sm0,2Ce0,8O2-?

• Main Author: Gunawan
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/35437
• Institution: Institut Teknologi Bandung

Fuel cells are electrochemical cells that convert chemical energy in fuels into electrical energy. Fuel cells have the same working principles with voltaic cells in terms of conversion of chemical energy into electrical energy. The difference lies in the continuity of electric energy production. Like combustion engine, fuel cells can continuously produce electricity as long as fuel is supplied into the cells. However, fuel cells have higher efficiency than combustion engines because the chemical energy is directly converted into electrical energy without conversion into kinetic energy. Solid oxide fuel cell is a type of fuel cell that uses oxide ceramic membrane as an electrolyte. In solid oxide fuel cells, oxide ions migrate from the cathode to the anode through the oxide ceramic membrane. Oxide ions are generated from oxygen gas reducted at the cathode. When they reached the anode, oxide ions will react with the fuel (H2) yields H2O and electrons flowing through the outer circuit. Electrical current are caused by the electron flow. Morphology of the electrolyte membrane is one factor affecting the performance of solid oxide fuel cells. Electrolyte membrane should have high density to prevent leakage of gas and low thickness to streamline the migration of oxide ions in the electrolyte membrane. Ceramic membrane with these criteria can be obtained through sintering of powder which has high sinterability. In this research, we have deposited SDC as electrolyte on La0,8Sr0,2MnO3-? - Sm0, 2Ce0,8O2-? (LSM-SDC) composite cathode. Oxide compounds are synthesized by means of coprecipitation and solid state reaction method. Characterization of oxide compounds have also been carried out which include the determination of crystal structures by X-ray diffraction method and electric conductivity by impedance spectroscopy. We have synthesized SDC using coprecipitation method to obtain nanoparticle SDC. Ammonia was used as reagent to precipitate Sm3+ and Ce3+ as samarium and cerium hydroxide. The produced precipitate was dried and calcined to obtain the SDC powder. Oxidation of Ce3+ to Ce4+ took place in this stage. The powder particle size produced by this method is 9,87 nm as calculated by Debye – Scherrer equation. This powder tend to form agglomerate as indicated by SEM image. Colloid SDC was obtained by dispersing it in water or acetone. Colloids are stable within a certain timeframe and deposited on LSM-SDC substrate through filtration and evaporation process. The deposited layers were fired at 1400 °C to obtain dense ceramic membrane with a thickness of 87,5 and 151 ?m as indicated by SEM image. Powder X-ray diffraction was carried out to determine the crystal structure of the synthesized oxide compounds. The diffractogram was analyzed by Le Bail method to determine the crystal structure of the synthesized oxides including its space group and lattice parameters. It is shown that Sm0,2Ce0,8O2-? has a cubic structure with space group and and for powder sythesized by coprecipitation and solid state reaction respectively. La0,8Sr0,2MnO3 has a hexagonal structure with space group and . Peak broadening obtained in the diffractogram of SDC synthesized by coprecipitation method arises from size effect. Whereas in SDC synthesized by solid state reaction, it arises from mictrostrain in lattice. Electrical conductivity was studied using electrochemical impedance spectroscopy. Electrical conduction consist of two different mechanism at 200 – 300 °C and 320 – 500 °C. Electrical conductivity of SDC layer synthesized by means of solid state reaction and coprecipitation method is 5.16 x 10-4 and 1.50 x 10-3 S.cm-1 respectively.