AGING PHENOMENON OF STABILIZED BISMUTH OXIDES

Stabilized bismuth oxides exhibit a decay in conductivity when anneale d at temperatures below 600-degrees-C. We refer to this phenomenon as aging and it is distinct from a conventional crystallographic phase tr ansformation. This phenomenon is revealed by an endotherm from DSC the rmal analysis and results in the formation of a superstructure observa ble by TEM diffraction patterns, yet no change in structure is observa ble by XRD. Since oxygen vacancies are the mobile defects responsible for ionic conductivity, we attribute the aging process to the ordering of oxygen vacancies by an order-disorder transition below approximate ly 600-degrees-C.