STUDY ON CHARACTERISTICS OF ZrO2-Y2O3-CeO2-Gd2O3 SYSTEM AS MATERIAL FOR SOLID ELECTROLYTE OF FUEL CELL

• Main Author: PRAMITASARI (NIM 13704027), DEVIANA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/10214
• Institution: Institut Teknologi Bandung

Solid Oxide Fuel Cell (SOFC) is a typical fuel cell which utilizes advanced ceramic technology particularly as solid electrolyte. Material commonly used for this kind of electrolyte is zirconia in stabilized using 8% mol of Y2O3. Unfortunately, this electrolyte consist of zirconia and Y2O3 has a low ionic conductivity, so it is necessary to add two kinds of doping agents, i.e. CeO2 and Gd2O3 in order to increase the ionic conductivity of the electrolyte.<p>Zirconia used in this experiment was obtained from processing of zircon opacifier as by a product of the concentrate separation at PT Timah, Bangka. Zirconia and doping agents were mixed and followed by compaction at the pressure of 30 kN resulting pellets with a diameter of about 1.39 cm. Four samples has been studied, e.g: sample-1 with a composition of [25% Gd2O3 : 75% (CeO2+YSZ)]; sample-2 [50% Gd2O3 : 50% (CeO2+YSZ)]; sample-3 [75% Gd2O3 : 25% (CeO2+YSZ)] and sample-4 [100% Gd2O3 : 0% (CeO2+YSZ)]. The sample was then sintered at temperature of 1400 oC for three different sintering times: 1, 2 and 3 hours. Samples were analyzed for the characteristic of shrinkage as well as its mechanism during the sintering. Sample obtained after sintering was analyzed for its ionic conductivity using Ultra High Resistance Meter.<p>Sintering in sample-3 was observed to be dominated by mass transfer by grain boundary lattice diffusion mechanism with the value of n of 5. Unfortunately, mass transfer mechanism in sample-1, sample-2 and sample-4 could not be determined, due probably to the multi-component mass transfer mechanism. Sample-3 showed a highest densification up to 30.59% (obtained from sintering for 3 hours), while highest densifications of sample-1, sample-2 and sample-4 were 23.64% (2 hours), 20.63% (1 hour) and 29.72% (2 hours) respectively. Sample-3 also showed a highest ionic conductivity of about 1.0861 x 10-6 S.cm-1 (obtained from sintering for 3 hours). All samples showed a more or less similar dependency of ionic conductivity on temperature, i.e. follows to Arrhenius type equation: k = so.exp{-Ea/(kT)} with a value of Ea in the order of magnitude of 10-20. The value of so depended on composition and sintering condition. The highest value of so in the range of 135-4720 S.cm-1 was found in sample-4. These experiments showed that samples with three doping agents had ionic conductivity higher than that with a single doping agent Y2O3 obtained in experiments by previous researcher. These experiments also revealed that the use of two doping agents, Y2O3 and CeO2, did not increase ionic conductivity significantly compared to that with a single doping agent.