Electron microscopy of phase boundaries between the A15 and D8_m, structures of Nb-ge

Abstract

The orientation relations along phase boundaries between grains of the cubic A15-phase and the tetragonal D8_m-phase in the Nb-Ge system have been investigated in polycrystalline films by high-resolution electron microscopy and selected-area electron diffraction techniques. Two of the three orientation relations found between the two phases are described in detail. The characteristic properties of these phase boundaries are interpreted using phase boundary theories by Bonnet and Durand and by Takata, Kitano and Komura. Since the characteristic geometrical data of these phase boundaries correspond to those in the V-Si system, it is concluded that they are caused by the geometrical relations between the two phases rather than by chemical factors.