Electron diffraction study of tysonite phases La1–ySryF3–y (0 ≤ y ≤ 0.15)

Abstract

Electron diffraction combined with simultaneous analysis of elemental composition in a transmission electron microscope is used for the first time to investigate La_1–ySr_yF_3–y (0 ≤ y ≤ 0.15) phases with tysonite structure (LaF₃). The two-phase structure of samples with y = 0.10 and 0.15 containing a tysonite matrix and thin interlayers of a phase with a structure similar to that of sphalerite is revealed. The two-phase state is presumably also present in a sample with y = 0.075; however, its content of the platelike phase is too small to be detected via electron diffraction. The presence of the platelike phase in the samples with y = 0.075, 0.10, and 0.15 explains the drop in fluorine ionic conductivity from its maximum at y = 0.05.