INCOMMENSURATE-COMMENSURATE PHASE-TRANSITION OF BAZNGEO4 STUDIED BY ELECTRON-MICROSCOPY AND DIFFRACTION

BaZnGeO4 undergoes several successive phase transitions from I to V phase. The modulated structure in the incommensurate phases (III and IV) and the commensurate-incommensurate phase transition between the IV and V phases were studied by electron microscopy. The direction of the modulation wave vector slightly deviates from the c* direction, and the tilt angle changes with temperature. The modulated structure does not change into the discommensuration (DC) arrays around the III' phase, but the DC's appear in the IV phase near the C-IC phase transition temperature. The electron microscope images clearly revealed that the stripples and antistripples composed of the three DC's were formed and moved in the DC lattice during the C-IC phase transition.