Ferroelectric domain configurations in 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 thick films determined by piezoresponse force microscopy

The spatial distribution of the out-of-plane and in-plane components of ferroelectric polarization in (1 - x) Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) thick films with x = 0.35 on Al2O3 substrates has been studied by piezoresponse force microscopy. Complex non-180 degrees domain configurations with strong variations in characteristic length (from micrometre size down to the nanoscale) and morphology are found. This is most probably the result of the slowing down of the kinetics of the relaxor to ferroelectric transition on approaching a grain size around the micrometre, an effect previously reported for bulk ceramics and that results in the stabilization of submicrometre and nanoscale intermediate domain configurations. Nevertheless, fluctuations of the in-plane compressive stress exerted by the substrate must exist and play a role, as indicated by in-plane polarization regions next to grain boundaries. Film stress might also be responsible for conventional 180 degrees domains not being found, and for the appearance of 180 degrees superdomain bands formed from bundles of submicrometre-size non-180 degrees domains instead, as previously described in Pb(Zr,Ti)O-3 films. Also, the presence of polar nanodomains and the possibility of them being observed are addressed. Finally, the mobility of non-180 degrees domain walls under electric fields is clearly demonstrated, which is the key to relatively high electromechanical response in films.