Solid‐State Reaction Kinetics of LaCrO3 from the Oxides and Determination of La3 +  Diffusion Coefficient

Abstract

The parabolic rate constant for the solid-state reaction of 1/2La2O3 + 1/2Cr2O, = LaCrO3 was measured at temperatures between 1483 and 1688 K in air and at 1695 K in oxygen pressures between 2.1 X i0 and 1.5 X 10 Pa. According to Wagner's theory, the diffusion coefficient of La in LaCrO3 was evaluated using the parabolic rate constant and the standard Gibbs energy change of the reaction. The oxygen pressure dependence of the diffusion coefficient is given by D,s./m2 s' = 4.5 X l0' (P02/Pa)31'6 a03 + 1.6 x 1016 a0 (T = 1695 K)where acr,o is the activity of Cr203 and P0 is the oxygen pressure. The temperature dependence of the diffusion coefficient of lanthanum ion in LaCrO3 is given by 2 -' -l ( 480 kJ mol' 316 18 D /m s = a3 x 10 expl -

Sintering kinetics and oxide ion conduction in Sr-doped apatite-type lanthanum silicates, La9Sr1Si6O26.5

“…(1) and (2), with n = 4 between 1350 and 1400°C, allows calculating an activation energy of 468 kJ/mol. This evaluated value should be consistent with the activation energy calculated for the diffusion of the rare-earth element, La in the perovskite LaCrO 3 (i.e Ea = 480 kJ/mol [26]). Furthermore, the presence of La 3+ vacancies in the 4f nine coordinated site of the apatite structure has been observed by neutron powder diffraction [18,27].…”

134Ba diffusion in polycrystalline BaMO3 (M = Ti, Zr, Ce)

“…13 The Ba lattice diffusion in BaMO 3 compared to the A-site cation diffusion in general in perovskites reported in the literature revealed no apparent trend. [26][27][28][29][30][31][32][33][34][35][36][37][38] In addition, the diffusion mechanisms for the data reported in the literature are usually not described. The point defect chemistry after materials processing determines the dominating diffusion mechanism as shown for BaZrO 3 .…”

Determination of inter-diffusion coefficients for the A- and B-site in the A2BO4+δ (A = La, Nd and B = Ni, Cu) system

“…One exception to this is LaCrO 3 [48] where La has higher diffusivity. However, the Asite diffusivity in the LNO system is rather high even when compared with the relatively high diffusivities of B-site cations in the other perovskite systems.…”