Ln molybdates are promising materials for hydrogen/oxygen separation membranes. This work aims at elucidating features of oxygen transport in Ln₁₀Mo₂O₂₁ (Ln = Nd, Ho) oxides using novel 2D diffusion models. Nd₁₀Mo₂O₂₁ and Ho₁₀Mo₂O₂₁ were synthesized by the mechanical activation followed by sintering in the 1600–1650 °C temperature range and characterized by XRD as a complex rhombohedral phase and fluorite one, respectively. Oxygen transport features were studied by the oxygen isotope heteroexchange with C¹⁸O₂ in a flow reactor using temperature-programmed and isothermal modes.

According to numerical analysis, isotope exchange in Ln₁₀Mo₂O₂₁ cannot be described by a single diffusion coefficient, which is explained by nonuniformity of the oxygen diffusion pathways. The mathematical model including equations for a faster diffusion along grain boundaries and a slower diffusion within grain bulk (2D diffusion model) gives the best fit. The same accuracy was achieved using the model including 2D diffusion and exchange between grain bulk oxygen forms with different M-O bonds strength. The values of oxygen tracer diffusion coefficient are ~10⁻⁷–10⁻⁶ cm²/s and ~10⁻¹¹–10⁻⁸ cm²/s at 700 °C along grain boundaries and within grain bulk, respectively. Hence, new 2D models were developed to describe oxygen diffusion in polycrystalline oxides. A fast oxygen diffusion demonstrated for Ln₁₀Mo₂O₂₁ oxides makes them promising for design of hydrogen/oxygen separation membranes.

钼酸镧是用于氢/氧分离膜的有前途的材料。这项工作旨在使用新颖的二维扩散模型阐明Ln ₁₀ Mo ₂ O ₂₁（Ln = Nd，Ho）氧化物中的氧传输特征。通过机械活化合成Nd ₁₀ Mo ₂ O ₂₁和Ho ₁₀ Mo ₂ O ₂₁，然后在1600-1650°C的温度范围内烧结，并通过XRD分别表征为复杂的菱面体相和萤石相。通过氧同位素与C ¹⁸ O _2的交换研究了氧的传输特征 在流动反应器中使用程序升温和等温模式。

根据数值分析，Ln ₁₀ Mo ₂ O _21中的同位素交换不能用单一的扩散系数来描述，这可以用氧扩散路径的不均匀性来解释。数学模型包括沿晶粒边界更快扩散和在晶粒体积内较慢扩散的方程式（2D扩散模型）提供了最佳拟合。使用包括二维扩散和具有不同MO键强度的颗粒体氧形式之间的交换的模型，可以实现相同的精度。氧示踪剂扩散系数的值为〜10 ^-7 –10 ^-6  cm ² / s和〜10 ^-11 –10 ^-8  cm ²/ s分别在700°C时沿晶界和在晶粒内。因此，开发了新的2D模型来描述氧在多晶氧化物中的扩散。Ln ₁₀ Mo ₂ O ₂₁氧化物具有快速的氧扩散性能，使它们有望用于氢/氧分离膜的设计。