Reduction in sintering temperature for flash-sintering of yttria by nickel cation-doping

Abstract 1 mol% Ni 2+ -doped Y 2 O 3 shows flash-sintering at DC fields greater than 300 V/cm. When compared to the undoped Y 2 O 3 , the onset temperature for the flash event is reduced by about 200 °C due to the Ni-doping. The electric conductivity during the sintering experiments for the Ni-doped Y 2 O 3 begins to increase above those of the undoped Y 2 O 3 at temperatures greater than 700 °C, then steeply rises corresponding to the flash event. Electron energy loss spectrometry (EELS) measurements indicated that Y 2 O 3 is highly reduced by the combination of the Ni-doping and flash-sintering as well as by conventional sintering in a reducing atmosphere. The applied electric field must involve the formation of oxygen anion vacancies and liberated electrons, and consequently, enhances the diffusional mass transport and electronic conduction in the Y 2 O 3 . The enhanced flash-sintering in the Ni-doped Y 2 O 3 must be attributed to an avalanche of the vacancy-electron pairs facilitated by the Ni-doping.