Effect of sintering aids on sintering kinetic behavior of praseodymium doped ceria based electrolyte material for solid oxide cells

Abstract

The present study investigates the effect of sintering additives (Li, Co, Fe, and Mg) on the sintering kinetic behavior of the praseodymium-doped-ceria (PDC) electrolyte of solid oxide electrolyzer cell. 3Li-PDC, 3Co-PDC, 3Fe-PDC, and 3 Mg-PDC pellets were obtained from the synthesis of PDC nano-powder by microwave-assisted co-precipitation method using isopropyl alcohol as a solvent and followed by sintering additive wetness impregnation method. Linear shrinkage and shrinkage rate data suggest a positive sintering effect for 3Li-PDC and 3Co-PDC pellets and a negative sintering effect for 3 Mg-PDC and 3Fe-PDC pellets than compared to PDC pellets alone. The addition of lithium as a sintering additive (3Li-PDC) had reduced the sintering temperature of PDC from 1100 °C to 850 °C. For PDC, 3Li-PDC, 3Co-PDC, 3Fe-PDC and 3 Mg-PDC pellets sintered at 1100 °C, 850 °C, 1000 °C, 1200 °C, 1100 °C for 2 h resulted in a relative density of 93.6 ± 0.25, 95.8 ± 0.45, 95.0 ± 0.20, 92.7 ± 0.10, and 94.5 ± 0.10%, respectively. The XRD patterns of the sintered PDC pellets suggested a secondary phase formation (PrO<inf>2</inf>) in 3Co-PDC, 3Fe-PDC, and 3 Mg-PDC pellets indicating that the addition of these sintering aids results in poor solubility limit of Pr in CeO<inf>2</inf>. On the other hand, XRD patterns of PDC and Li-PDC sintered pellets displayed no secondary peak indicating good solid-solution formation. The activation energy of the 3Li-PDC pellet is obtained from CHR and Dorn methods and was found to be 182 kJ/mol and 196 kJ/mol. From the CHR method, for the 3Li-PDC pellet, the initial sintering behavior is by the grain boundary diffusion mechanism (m = ~2). © 2020 Hydrogen Energy Publications LLC