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Voltage‐Controlled Nonstoichiometry in Oxide Thin Films: Pr 0.1 Ce 0.9 O 2−δ Case Study
Author(s) -
Chen Di,
Tuller Harry L.
Publication year - 2014
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201402050
Subject(s) - materials science , stoichiometry , yttria stabilized zirconia , thin film , oxide , oxygen , analytical chemistry (journal) , dielectric spectroscopy , isothermal process , oxygen sensor , cubic zirconia , biasing , electrochemistry , electrode , nanotechnology , voltage , chemistry , composite material , thermodynamics , electrical engineering , ceramic , physics , organic chemistry , chromatography , engineering , metallurgy
While the properties of functional oxide thin films often depend strongly on oxygen stoichiometry, there have been few means available for its control in a reliable and in situ fashion. This work describes the use of DC bias as a means of systematically controlling the stoichiometry of oxide thin films deposited onto yttria‐stabilized zirconia substrates. Impedance spectroscopy is performed on the electrochemical cell Pr 0.1 Ce 0.9 O 2−δ (PCO)/YSZ/Ag for conditions: T = 550 to 700 °C, pO 2 = 10 −4 to 1 atm, and ΔE = ‐100 to 100 mV. The DC bias ΔE is used to control the effective pO 2 or oxygen activity at the PCO/YSZ interface. The non‐stoichiometry ( δ ) of the PCO films is calculated from the measured chemical capacitance ( C chem ). These δ values, when plotted isothermally as a function of effective pO 2 , established, either by the surrounding gas composition alone, or in combination with applied bias, agree well with each other and to predictions based on a previously determined defect model. These results confirm the suitability of using bias to precisely control δ of thin films in an in situ fashion and simultaneously monitor these changes by measurement of C chem . Of further interest is the ability to reach effective pO 2 s as high as 280 atm.