The defect structure of hard Cu-modified polycrystalline PbTiO3 ferroelectrics was investigated by means of electron paramagnetic resonance and hyperfine sublevel correlation spectroscopy, as well as density functional theory calculations. Special emphasis was put on the 207Pb-hyperfine couplings, which were resolved up to the third coordination sphere. The results prove that Cu was incorporated at the octahedrally coordinated Ti site, acting as an acceptor. Because of charge compensation the formation of Cu impurity–O vacancy pairs was energetically very favorable. The corresponding (CuTi”-VO••)x defect dipole was found to be oriented along the [001] axis.

Defect-Dipole Formation in Copper-Doped PbTiO3 Ferroelectrics. R.A.Eichel, P.Erhart, P.Träskelin, K.Albe, H.Kungl, M.J.Hoffmann: Physical Review Letters, 2008, 100[9], 095504