Densification of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ ceramic by flash sintering at temperature less than 100 °C

The effect of DC electric field on sintering and electrical conductivity of La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF), considered as highly promising cathode material for solid oxide fuel cell, is investigated in the present work. It is shown that sintering can be carried out at (furnace) temperature <100 °C under electric field ranging from 7.5 to 12.5 V/cm; such extraordinary effect is associated with the high electrical conductivity of LSCF through a peculiar mechanism. Microstructural analysis suggests similar morphology and enhanced grain growth compared to traditional sintering; with the proper choice of processing parameters (electric field and current density) during flash sintering, homogeneous porous microstructure for cathodic application can be obtained in very short time. The role of electric field and specimen temperature in flash sintering is analyzed for the understanding of observed outstanding event. The conductivity is found to be a coupled response of electric field and temperature; 2–3 V/cm and 15–25 °C are sufficient for dense LSCF specimen to stimulate the electric field effect on sintering. Electric field controls the conductivity in the same way as temperature does suggesting that under flash effect conductivity is increased by usual mechanism. On the same basis, flash sintering is proposed to be accelerated by the “polaron hopping” phenomenon.