Thermodynamics and diffusivity of yttrium in yttrium chromite (YCrO₃)

The Standard Gibbs energy change of the following reaction, (1/2)Y₂O₃+(1/2)Cr₂O₃ = YCrO₃, was determined as ΔG° /J mol^-1 = -7.25×10⁴+2.69×10T±2.1×10³ using oxygen concentration cells, and taking into account the partial electronic conduction in solid electrolyte of stabilized zirconia. Wagner's theory, provides the diffusivity of the rate limiting species in a solid state reaction when the Gibbs energy change of the reaction is available. The solid state reaction between single crystals of Y₂O₃ and Cr₂O₃ gave polycrystalline YCrO₃ and the reaction rate was limited by the diffusion of a yttrium ion in YCrO₃. With the information of the possible defect structure in YCrO₃, Cr₂O₃+3/2O₂→2Vqq_Y+2Cr_Cr^x+6O _O^x+6h the diffusion coefficient of a yttrium ion in YCrO₃ is obtained using solid state reaction at 1458 to approximately 1719 K in the air. D_Y(3+)/m²s^-1 = [8.36×10^-9 exp (-272/kJ mol^-1/RT)] P_O(2)^3/16a_Cr(2)O(3)^1/8, where a_Cr(2)O(3) is the activity of Cr₂O₃ and P_O(2) is the oxygen pressure.