Chemical diffusion coefficient measurements in pure and lithium doped cobaltous oxide

Abstract

The chemical diffusion coefficient in pure and lithium doped cobaltous oxide has been deduced from electrical conductivity measurements performed during the equilibration of the gas-oxide system, in the temperature range 1000-1400° and for oxygen partial pressures higher than 10⁻⁵ atm.

The results obtained for the pure Co₁-δO single crystals show a small decrease of the values of the chemical diffusion coefficient with the oxygen partial pressure. Under air their variation with temperature can be expressed by the relation: [Dtilde] = 0.13 exp(-30.0) (k cal-mol-¹)/RT cm² sec⁻¹

The molar fraction of lithium in the two doped samples studied is, respectively, 5.13 10⁻³ and 11.8 10⁻³. Under air the variation of the chemical diffusion coefficient with temperature has been determined as: [Dtilde] = 0.014 exp(-27.0) (kcal mol⁻¹)/RT cm² sec⁻¹.

Lithium lowers the values of the chemical diffusion coefficient due to a decrease of the product v ₀ exp(δSm/R).