USE OF IN-SITU TEM EXPERIMENTS FOR PHASE-TRANSITION STUDIES

We present various in situ TEM experiments performed for phase transit ion studies. Such original experiments require original stages that ar e presented before each discussion. The first part concern TEM studies of ferroic domain switches carried out on ferromagnetic and ferroelec tric/ferroelastic compounds. Then we present in situ TEM experiments c arried out on the tetragonal-orthorhombic structural phase transition in YBa2Cu3O6+x under a controlled oxygen pressure. The last part of th e paper deals with the incommensurate phase of Quartz. We present TEM experiments concerning the triple-q to single-q phase transition that have been performed using an heating straining stage and other origina l results evidencing the ferroelectric properties of the incommensurat e phase.