Determination of Diffusion Coefficient of Nd3+ in NdCrO3 Based on Solid State Reaction.

概要

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The solid state reaction, (1⁄2)Nd2O3+(1⁄2)Cr2O3→NdCrO3, was studied between 1473 K and 1773 K in air to determine the parabolic rate constant. The electrical conductivity of the NdCrO3 phases separately equilibrated with Nd2O3 and Cr2O3 were measured between 1673 K and 1773 K in an argon-oxygen mixture. The standard Gibbs energy change for the solid state reaction was estimated from the activity dependence of the electrical conductivity of NdCrO3. According to Wagner's theory, the diffusion coefficient of Nd3+ in NdCrO3 can 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 diffusion coefficient of Nd3+ in NdCrO3 was given by D_Nd^3+/m^2s^-1 = 1.3 ×10^-6 ·exp\\left(-\\frac343 kJ mol^-1RT \\right) (P_O_2/Pa)^3/16 a_Cr_2O_3^1/8where aCr2O3 is the activity of Cr2O3 and PO2 is the oxygen pressure. The obtained diffusion coefficient of Nd3+ in NdCrO3 was compared with that of Y3+ in YCrO3 and that of La3+ in LaCrO3.
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