The solid-state reaction, (½)Nd2O3 + (½)Cr2O3 → NdCrO3, was studied between 1473 and 1773K in air in order to determine the parabolic rate constant. The electrical conductivity of the NdCrO3 phases, separately equilibrated with Nd2O3 and Cr2O3, were measured between 1673 and 1773K in an Ar-O mixture. The standard Gibbs energy change for the solid-state reaction was estimated from the activity dependence of the electrical conductivity of NdCrO3. Then, according to Wagner’s theory, the diffusion coefficient of Nd3+ in NdCrO3 could be evaluated from the parabolic rate constant for the solid-state reaction, the standard Gibbs energy change of the solid-state reaction and the defect equilibrium reaction in NdCrO3. From these data, the diffusivity of Nd3+ in NdCrO3 was found to be given by:

D (m2/s) = 1.3 x 10-6 exp[-343(kJ/mol)/RT] P3/16 a1/8

where P was the O partial pressure (Pa) and a was the activity of Cr2O3.

Determination of Diffusion Coefficient of Nd3+ in NdCrO3 Based on Solid State Reaction. T.Akashi, Y.Mizuno, M.Nanko, T.Maruyama, A.Saiki, K.Tsukui, J.Tanabe: Materials Transactions, 2001, 42[7], 1411-6