Electrical conductivity of Ca-doped YFeO₃

Abstract

Electrical conductivity and Seebeck coefficient of calcium-doped YFeO₃, a potential cathode material in solid oxide fuel cells (SOFC), are measured as function of temperature and composition in air to resolve conflicts in the literature both on the nature of conduction (<i style="mso-bidi-font-style:normal">n</i>- or <i style="mso-bidi-font-style: normal">p</i>-type) and the types of defects (majority and the minority) present. Compositions of Y_{1-<i style="mso-bidi-font-style:normal">x</i>}Ca<i style="mso-bidi-font-style:normal">_x</i>FeO_{3−<i style="mso-bidi-font-style:normal">δ</i>} with <i style="mso-bidi-font-style: normal">x</i> = 0.0, 0.025, 0.05 and 0.1 are studied in <span style="mso-bidi-font-style: italic">the temperature range from 625 to 1250 K. All Y_{1-<i style="mso-bidi-font-style:normal">x</i>}Ca<i style="mso-bidi-font-style: normal">_x</i>FeO_{3−<i style="mso-bidi-font-style:normal">δ</i>} samples show <i>p</i>-type semiconducting behaviour. <span style="mso-bidi-font-style: italic">Addition of Ca up to 5% dramatically increases the conductivity of YFeO₃; increase is more gradual up to 10%. A second phase Ca₂Fe₂O₅ appears in the microstructure for Ca concentrations in excess of 11%.

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