Reaction kinetics in the system Y2O3/Al2O3 - Use of an external electric field to control the product phase formation in a system forming multiple product phases

This study investigates the influence of an external electric field on the kinetics of a heterogeneous solid state reaction between Al2O3 and Y2O3. The reaction couples were prepared by means of pulsed laser deposition (PLD) by growing Y2O3 films on single crystalline alumina substrates with an (0001) orientation. The solid state reaction was performed at a temperature of 1400 (1673 K). Utilising attached platinum electrodes, an electric field of 350 V/mm was applied. The superposed field led to an ionic current through the reacting sample and modifies the individual growth kinetics of the three product phases/layers, Y3Al5O12 (YAG), YAlO3 (YAP) and Y4Al2O9 (YAM) The cross-sections of the reacted samples were characterised by means of SEM and XRD. Depending on the direction of the ionic current, the kinetics of the YAP phase formation in particular was strongly influenced. The general kinetics of a solid state reaction forming multiple product phases was analysed using linear transport theory. The effect of an electric field for controlling the product phase formation to prefer or to kinetically suppress the formation of a distinct phase is demonstrated.