Investigation on flash sintering of BaZr0.1Ce0.7Y0.2O3-δ compound; using nickel wire as electrode material

Abstract In this work, flash sintering of BaZr0.1Ce0.7Y0.2O3-δ (BZCY7) compound for the first time has been investigated. The BaZr0.1Ce0.7Y0.2O3-δ powder was synthesized via the solid state reaction method. Nickel wire was selected as electrode material, as it had the required properties to perform a reversible electrochemical reaction with the BZCY7 compound. Different DC electric fields of 500, 400, 300, 200 and 100 V/cm were examined, and the relationship of Tonset = 2626 × E-0.221 between the onset temperature of flash sintering and the applied electric field was found. Using this equation, a critical electric field of 28.75 V/cm for transition from FAST (field-assisted sintering technique) to flash sintering regime, for the BZCY7 compound was estimated. From microstructural studies and the determined linear shrinkage of specimens, it was found that high enough electric fields could hinder grain growth, however, they may cause poor densifications. Different current density limits of 125, 100, 75, 50 and 25 mA/mm2 at a given electric field were also examined, and it was found that current density was directly and significantly related to densification, grain size and the estimated temperature of the specimens. To study the effect of long holding times on grain growth, a sample was kept under an applied electric field of 200 V/cm and the current density limit of 125 mA/mm2 for 6 min. FE-SEM micrograph of this sample showed formation of grains, as large as 70 μm and even more.