Evaluation of high-temperature electronic and electrochemical properties of the strained La 1-x Sr x CoO 3-δ films prepared by a pulsed laser deposition technique

Takashi Nakamura, Daisuke Hemmi, Katsutoshi Iwamoto, Nobuyuki Hirai, Maya Sase, Atsushi Unemoto, Fumimasa Horikiri, Yoshihiro Mori, Kazuhisa Sato, Keiji Yashiro, Tatsuya Kawada, Junichiro Mizusaki

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

To evaluate the electrochemical and electronic properties of strained film specimen, La 1-x Sr x CoO 3-δ (x = 0.4, 0.5) films were evaluated by means of electrochemical impedance spectroscopy and electrical conductivity measurement. Dense polycrystalline La 1-x Sr x CoO 3-δ films were fabricated on a polycrystalline Ce 0.9 Gd 0.1 O 1.95 substrate by a pulsed laser deposition technique. Obtained film was (001) oriented in the pseudo-cubic perovskite unit cell and tensile strained along out-of-plane direction. It was confirmed that oxygen nonstoichiometric behavior of the film was different from that of bulk La 1-x Sr x CoO 3-δ and analyzed by assuming localized and itinerant electronic states. Localized electron model with Co 2+ , Co 3+ and Co 4+ shows good agreement with observed oxygen nonstoichiometry of the film. The electrical conductivity of La 1-x Sr x CoO 3-δ films show positive temperature coefficient like semiconductors although that of the bulk La 1-x Sr x CoO 3-δ shows a negative temperature coefficient like metals. This indicates localized electron for the La 1-x Sr x CoO 3-δ film and itinerant electron for the bulk La 1-x Sr x CoO 3-δ . Although detail mechanism of the strain effect is not fully understood, both oxygen nonstoichiometric and electronic conduction behaviors of the film could be explained by assuming localized electronic state. Plausible electronic structure of the film was proposed and compared with that of bulk La 1-x Sr x CoO 3-δ .

Original languageEnglish
Pages (from-to)884-890
Number of pages7
JournalElectrochemistry
Volume82
Issue number10
DOIs
Publication statusPublished - 2014 Jan 1

Keywords

  • La Sr CoO film
  • Oxygen nonstoichiometry
  • PLD
  • Strain

ASJC Scopus subject areas

  • Electrochemistry

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