Abstract

The electron diffraction investigation of two-component phases in the systems MF₂–RF₃ (CaF₂–ErF₃, SrF₂–LaF₃) and components of the systems CaF₂, SrF₂, BaF₂, and LaF₃ is performed in a transmission electron microscope. The effect of electron irradiation, causing decomposition of metal fluorides with elimination of fluorine and transformation of the formed metal into oxide, is demonstrated. The crystal structure of the ordered tysonite (structural type LaF₃) phase of the composition Er_0.7Ca_0.3F_2.7, characterized by complete cation ordering and a low fluorine-ion conductivity, is identified. A nanostructured state of the tysonite phase La_1 – ySr_yF_3 – y (y = 0.10, 0.15), comprised of a tysonite matrix and lamellar interlayers of a phase enriched with strontium, is established. The formation of lamellar interlayers is responsible for the decrease in the ionic conductivity of the tysonite phases La_1 – ySr_yF_3 – y with an increase in the content of strontium after the conductivity peak at y = 0.05.

中文翻译：

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系统 MF2-RF3（CaF2-ErF3、SrF2-LaF3）中相结构的电子衍射研究

摘要

M F ₂ – R F _{3 系统}（CaF ₂ –ErF ₃、SrF ₂ –LaF ₃）和系统CaF ₂、SrF ₂、BaF ₂和LaF ₃的组分中的双组分相的电子衍射研究是在透射电子显微镜中进行。证明了电子辐射的影响，导致金属氟化物分解，消除氟并将形成的金属转化为氧化物。Er _0.7组成的有序泰森石（结构类型 LaF ₃）相的晶体结构Ca _0.3 F _{2.7 的}特点是完全的阳离子有序和低氟离子电导率。建立了由 tysonite 基体和富含锶的相的层状夹层组成的 tysonite 相 La _{1 –  y} Sr _y F _{3 –  y} ( y = 0.10, 0.15)的纳米结构状态。层状夹层的形成是导致 tysonite 相 La _{1 –  y} Sr _y F _{3 –  y}的离子电导率降低的原因，在y = 0.05处的电导率峰值之后锶含量增加。