A CRYSTALLOGRAPHIC ANALYSIS OF THE MACRODOMAIN STRUCTURE IN PB(MG1 3NB2/3)O-3/

A crystallographic analysis of the ferroelectric/ferroelastic domains and phase boundaries in thin platelets of Pb(Mg1/3Nb2/3)O-3, associate d with the electric-field-induced phase transition from the disordered cubic phase to the induced 3m phase, is reported. Calculations have b een performed by taking into account the internal stresses and their r elation to the unit cell parameters. The results have permitted us to interpret the experimentally observed polar macrodomain structure, pha se boundary and switching of the induced polarization. A diagram conne cting the possible domain types and the shapes of the m(3) over barm$ reversible arrow 3m phase boundaries has been proposed. The role of th e several domain types and features of their elastic matching have als o been analysed.