Influence of electric current on microstructure and electrical property of Al-doped ZnO ceramic consolidated by spark plasma sintering

Electrical current passing through SPS-ed Al-doped ZnO (AZO) ceramic in four conditions with same heating rate and dwell time has been conducted to investigate the influence of current on microstructure and electrical property. The applied current and thermal distribution of AZO ceramic are analyzed by finite element modeling. The local microstructure and electrical property of SPS-ed AZO in center and edge has been discussed in comparison. It is indicated that current density determines the thermal distribution and the coupling effects of current/thermal significantly influence the grain size, impurity phase ZnAl₂O₄ and dislocation defects. The increased current density contributes to the refinement of grain size and enhancement of impurity ZnAl₂O₄ which dramatically affects the resistivity. The elevated Hall mobility of SPS-ed AZO ceramic by the reduction of current density is mainly governed by weakening grain boundary scattering due to the enlarged grain size, which is confirmed to be the crucial factor on the variation of resistivity. The lowest resistivity of 6.1 × 10⁻⁴ Ω cm for SPS-ed AZO ceramic is achieved with extremely low current density passing through specimens.