Platinum Electrodes and Calcia-Stabilized Zirconia

Abstract

Measurements of the direct current-voltage characteristics of calcia-stabilized zirconia using platinum electrodes of various types have been made to investigate possible electrode processes. Depending on the form of the electrode, the rate-limiting step in the electrical conduction sequence can be (a) ionic conduction by O = in the zirconia, (b) electronic conduction in the zirconia, (c) oxygen atom diffusion through the platinum cathode, (d) the transfer of oxygen from the gas phase into the zirconia at the zirconia-gas interface on the cathode side. The conditions, under which each of these situations exists, are explained in terms of the structure of the electrode.Earlier studies on cells Pt, 02[0.85 ZrO2 9 0.15 CaOIPt, 02 with platinum point electrodes (1), or porous platinum electrodes (2), showed the I-V characteristic to be markedly nonohmic. The rate-controlling step responsible for this behavior was found to be confined to the cathode. Two mechanisms of electrode operation appeared to be important (2). At low voltages (e.g., * Electrochemical Society Active Member.

Electronic conductivity in La1−xBaxF3−x crystals

“…Such a large value of a has been observed many times before and has, amongst others, been ascribed to partial blocking of the ionic current [21,25]. Brook et al [24] have considered a relaxed requirement of complete blocking of ions at the inert interface, in that a residual ionic current Iir is allowed for. This requirement is valid under the condition that Iir "~Iio, the ionic current in the absence of polarization.…”

Electrical polarization of lead bromide crystals. I

“…The electron current reaches its limiting value at eE/kTB 1. In the case that excess electron conduction is negligible we can write as an approximation log i, cz (16) if eE/kT$-1.…”

N-type Conductivity in Stabilized Zirconia Solid Electrolytes

“…Ionic current is blocked and a plot of log electronic current against applied potential can be used to obtain the n-type conductivity at the oxygen pressure defined by the reversible reference electrode (11,18,19). By consequence of the proportionality between r and Poe -1/4 and available ionic conductivity data (3), P0 can be determined.…”

“…[19] followed again by integration across the electrolyte from x = 0 at the anode to x = L at the cathode produces Eq. [18]. From Eq.…”

“…[7] and [8] in a recent paper (29). For almost complete ion blocking, an approximate expression for in has been derived (18).…”