A Study on Sintering Behaviour of Praseodymium Doped Ceria Based SOFC Electrolytes

Abstract

The present study explores the sintering kinetic behaviour of the Praseodymium doped ceria (PDC, Ce0.9Pr0.1O2) based Solid Oxide Fuel Cell (SOFC) electrolyte materials synthesized by various methods like the EDTA-citrate method, Microwave assisted co-precipitation method (using solvents like ethanol, water and iso – propyl alcohol) and room temperature co-precipitation method and are characterized by X- Ray Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) analysis and Dilatometer studies. By synthesis approach, the sintering temperature of the PDC electrolyte materials is drastically decreased from 1500°C to 1100°C by achieving unimodal shrinkage rate behaviour at a much lower temperature from 1460°C to 765°C and successfully achieved single-phase cubic fluorite PDC solid-solution. Two sintering models (Constant Heating Rate (CHR) method and Dorn method) were successfully implemented to identify the mechanism for early stages of sintering and found that grain boundary diffusion mechanism (m ~ 2) is dominating in PDC pellets synthesized by the MWCOP-ISP method. The effect of liquid additives such as Li, Co, Fe and Mg on the sintering kinetic behaviour of PDC pellets synthesized by MWCOP-ISP is further studied and decreased the sintering temperature from 1100°C to 850°C with the Li liquid additive as a sintering aid. The two sintering models further suggested that the Li-PDC pellets also follow the grain boundary diffusion model (m ~ 2) during the early stages of sintering. The 10PDC, 1Li-PDC, 3Li-PDC, 3Co-PDC, 3Fe-PDC and 3Mg-PDC nano-structured samples exhibited a thermal expansion co-efficient of 15.3x10-6 / °C, 18.2x10-6 / °C, 14x10-6 / °C, 15.2x10-6 / °C, 13.8x10-6 / °C and 15.7x10-6 / °C respectively.