Measurement and finite element modeling of triple phase boundary-related current constriction in YSZ

Dense, photolithographically patterned platinum microelectrodes were created on yttria-stabilized zirconia (YSZ). The electrodes, typically tens of microns across, were orders of magnitude greater in width than that reported for the triple phase boundary width. Impedance spectra exhibited an additional feature at low frequencies that was believed to be due to a constriction resistance, where all of the current had to pass through a narrow triple phase boundary. The resistance of this feature had a similar activation energy to the conductivity of the electrolyte and was as large as nearly 100 times the high frequency resistance. Finite element models describing constricted and unconstricted resistances achieved qualitative agreement with the experimental results but consistently underestimated the constricted resistance. The implications of constriction upon the performance of micro-ionic devices and the potential for future similar measurements to quantify triple phase boundary widths are discussed.