Effect of Electric Field on Uniaxial Viscosity and Sintering Stress of Ceria

The production of traditional and advanced ceramics is an energy-intensive activity, which requires high temperatures and longer dwelling times to activate diffusional processes necessary for densification. Electric field assisted processing has received considerable attention recently, due to its potential to significantly reduce the costs of required heat treatments. However, the effect of electric fields on the densification and coarsening of oxide ceramics still not completely understood, and the mechanisms behind, in particular for fields, are still under debate. The potential influence of electric field on the sintering parameters (uniaxial viscosity and uniaxial sintering stress) and microstructure of polycrystalline yttria doped ceria were studied. Sintering parameters were measured without and with AC electric fields (14 V/cm and 28 V/cm, 50 Hz) which were below the "flash regime." During all sintering measurements, the sample temperature was adjusted by lowering the furnace temperature according to the temperature measurements using densified samples. Major findings are: (i) The densification behavior is clearly modified by these moderate electric fields, although temperature increase due to macroscopic Joule heating is excluded. (ii) The densification rate remains proportional to the applied stress under electrical fields. (iii) Sintering parameters are significantly affected by the applied electric fields.