Point defects and high-temperature creep of non-stoichiometric NaCl-type oxide single crystals II. CoO

Abstract
High-temperature creep of CoO single crystals has been investigated by compression along 〈100〉 in the temperature range 0·6T m to 0·8T m, for stresses of 5 to 25 MPa and oxygen partial pressures pO2 from 10−5 to 0·2 atm. The stress exponent decreases from a value of 8·5 at low temperature to 6·5 at high temperature; the activation energy is 5 eV at pO2 = 10−5 atm and increases from 2·5 to 5 eV when the temperature increases in air, and the pO2, exponent decreases from 0·5 to 0·1 when the temperature increases. The steady-state creep of CoO appears to be controlled by oxygen diffusion. The mechanism of diffusion is governed by oxygen interstitials at low T and high pO2 and by oxygen vacancies at high T and low pO2.

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