Anomaly Negative Resistance Phenomena in Highly Epitaxial PrBa0.7Ca0.3Co2O5+δ Thin Films Induced from Superfast Redox Reactions

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Date
2021-11-26Author
Luo, Yumei
Xu, Xing
Xia, Yudong
Pang, Shengli
Xu, Fen
Whangbo, Myung-Hwan
Sun, Lixian
Chen, Chonglin
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Thin films of Ca-doped double perovskite, PrBa0.7Ca0.3Co2O5+δ (PBCC), were epitaxially
grown on (001) SrTiO3, and their redox reactions under a switching flow of H2 and O2 gases were
examined at various temperatures by measuring the resistance R(t) of the films as a function of the
gas flow time t. In the temperature range between 350 and 725 ◦C, these thin films are reduced and
oxidized in an ultrafast manner under the flow of H2 and O2 gases, respectively, suggesting that
PBCC thin films are promising candidates for developing ultra-sensitive oxygen sensors or SOFC
cathodes at intermediate or high temperatures. When the gas flow is switched to O2, the reduced
PBCC thin films exhibit a negative resistance at temperatures above 600 ◦C but a positive resistance
at temperatures below 600 ◦C. The probable cause for these anomalous transport properties is the
diffusion of the H atoms from the cathode to the anode in the PBCC film, which provides a current
opposite to that resulting from the external voltage.
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Physics and Astronomy
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