INTERMETALLIC PHASES AT THE CATHODICALLY POLARIZED INTERFACE PLATINUMPOLYCRYSTALLINE YTTRIA-STABILIZED ZIRCONIA/

A deep cathodic polarization has been applied to a Platinum/Polycrysta lline Yttria Stabilized Zirconia interface under low oxygen pressure. In the temperature range 973 - 1273 K the Electromotive Force recorded after the current cut off did not show any rest potential at a level corresponding to nucleation of a zirconium metal phase, likely because such process is kinetically unfavoured with respect to that of format ion of intermetallic phases, whose stability introduces a limitation o f the local oxygen chemical potential depression. Two rest potentials were found at less negative potentials which levels correspond to inte rmetallic phases which very high stability can be accounted for d-d or bitals bonding, as described by the Engel-Brewer correlation. In some EMF decays it was observed the occurrence of a third rest potential, l ocated at similar to -450 mV (reference pure oxygen) that could be att ributed to a transitory presence of a Pt-Zr-O phase.