Effect of microwave sintering on properties of Erbia stabilized bismuth oxide prepared by auto combustion method for IT- SOFC electrolytes

Abstract

Bismuth oxide based ceramics show the highest oxide ion conductivity even below 500 °C, they are expected to be promising material for solid electrolyte of IT-SOFC. Pure bismuth oxide however transforms to monoclinic phase on cooling below 730 °C. The cubic phase at high temperature can be stabilized down to room temperature by the additions of Erbia. In this work 20 mole% Erbia stabilized bismuth oxide (Bi0.8Er0.2O1.5) nano powder has been prepared by Citrate-Nitrate auto combustion method. Thermal analysis of as-synthesized powder is done by DTA /TGA. Powder is calcined at 700 °C for 4 hours and X-Ray diffraction pattern confirm the cubic phase bismuth oxide (JCPDS file 20-0052). Powder is compacted into pellets under 5 ton load and sintered using microwave furnace at 900 °C for 15 min. Density of more than 97% of theoretical value has been found. Impedance analysis shows higher ionic conductivity 0.035 S/cm at 500 °C which is 1.5 times more compared to conventional sintered samples sintered at 1000 °C. SEM analysis confirms uniform grain size with almost negligible porosity.