Abstract
The third-order Ruddlesden-Popper phase Pr4Ni2.7Co0.3O10-δ (PNCO43) was synthesized by a freeze drying process. Phase purity and crystal structure were determined by X-ray diffraction and Rietveld analysis. The electronic conductivity of a bulk sample obtained by a two-step sintering process was measured by the four-point dc van der Pauw method as a function of temperature (50 ≤ T/°C ≤ 800) and oxygen partial pressure (1 × 10−3 ≤ pO2/bar ≤1). Dense thin-film PNCO43 microelectrodes were prepared by pulsed laser deposition and photolithography on yttria-stabilised zirconia substrates. The thin-films were characterized by X-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy, and inductively coupled plasma optical emission spectroscopy. Individual resistive and capacitive processes were investigated with electrochemical impedance spectroscopy as a function of the oxygen partial pressure (1 × 10−3 ≤ pO2/bar ≤1) and temperature (600 ≤ T/°C ≤ 850). Oxygen surface exchange coefficients kq, calculated from the resistance of the electrode, show relatively high values (e.g. kq = 1.5 × 10−6 cm s−1 at 800 °C and 2 × 10−1 bar pO2). Chemical surface exchange coefficients kchem of oxygen were obtained from the peak frequency or the chemical capacitance as determined by impedance spectroscopy.
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