Microscopie et diffraction électroniques de couches minces de sesquioxyde de néodyme. La transformation de caractère martensitique phase monoclinique–phase hexagonale

Abstract

Thin films of neodymium metal are oxidized at low temperature into C-type Nd2O3. Under the electron-beam impact in the electron microscope, C-Nd2O3 recrystallizes to yield large crystals of the high temperature phase hexagonal A-Nd2O3. The plane of the thin A-Nd2O3 films is perpendicular to the c-hexagonal axis. In analogy with previous work on B-Sm2O3 thin films, the plane of the film is then parallel to the basal plane of the (LnO)n+n (Ln = rare earth) complex group in the A structure. A special treatment of the films allows the formation of thin bands of B-Nd2O3 structure in the A-Nd2O3 crystals. The two structures are in epitaxic continuity which is sometimes attained with the help of the same type of twinning as observed previously for B-Sm2O3. B-Nd2O3 bands disappear within minutes after formation and the B to A transformation exhibits a martensitic character.