Development of Solid Electrolyte Material Based on Zinrconia-Bismuth Oxide

Abstract

Solid electrolyte is very important part of the solid oxide fuel cell (SOFC). Currently the yttria stabilized zirconia is being used as an electrolyte material in SOFCs due to it’s high ionic conductivity. However, its ionic conductivity decreases drastically below temperature of 1000oC. Due to this reason, the researchers are concentrating on new materials which could possess high conductivity at low temperature. On the other hand, ZrO2 exhibit monoclinic structure which is stable from room temperature up to 1170oC only. The motivation of the present study was to stabilize high temperature ZrO2 cubic (high ionic conductivity) phase at low temperature by doping with Bi2O3. Various samples synthesized with composition of ZrO2 doped with Bi2O3 exhibits XRD pattern consisting of three main phase’s viz. Bi2O3, ZrO2 and Bi1.85Zr0.15O3.075. The electrical conductivity as well as thermal study of three samples with composition (15 mol% Bi2O3 with 85 mol% ZrO2, 20 mol% Bi 2O3 with 80 mol% ZrO2 and 25 mol% Bi2O3 with 75mol% ZrO2 ) was measured and change of one order of conductivity was observed in sample III due to higher disordering present in the sample. Moreover, the structural features of sample III comes out to be different from sample I and sample II. This variation arises due to the liberation of Bi2O3 phase from inner core of the sample which causes different structural features. Thus it can be concluded that ZrO2 cubic phase could not be stabilized at room temperature after doping with Bi2O3. The details of the study are presented in subsequent chapters.