DEFECT STRUCTURE AND ELECTRICAL CONDUCTIVITY OF La_(0.9)Ca_(0.1)Cr_(1-y)Al_yO_(3-δ) (y = 0 - 0.9)

摘要

Oxygen nonstoichiometry, δ, of La_(0.9)Ca_(0.1)Cr_(1-y)Al_yO_(3-δ) (y = 0.1, 0.2, 0.4, 0.6, 0.8, 0.9), was measured as a function of oxygen partial pressure, P_(O_2), by means of thermogravimetry at 1273K. The deviation from stoichiometry was observed in reducing atmospheres for all the samples. It started at higher P_(O_2) with increasing Al content. Electrical conductivity, σ, of La_(0.9)Ca_(0.1)Cr_(1-y)Al_yO_(3-δ) (y = 0.9) was also measured as a function of P_(O_2) by means of a.c. four-probe method. The conductivity is approximately two-orders-of-magnitude lower than that of doped lanthanum chromite, and close to that of doped lanthanum aluminate. The electronic current seems to be transported by hole which is trapped on Cr-site. Band conduction model of thermally activated holes explained the behavior of conduction better than hopping conduction model.