Phase transition and phonon characteristics of PbTiO_3 single-crystal nanorods prepared in NaCl flux

摘要

By annealing PbTiO_3 (PT) nanoparticles together with surfactants in NaCl flux, single-crystal PT nanorods were prepared with diameters of 60-80nm and lengths of several micrometers. The PT nanorods are in tetragonal phase and grow along the (100) direction. A first-order phase transition from tetragonal (a=3.922A and c=3.963A) to cubic (a =c =3.942 A) has been detected at 440°C. With the increasing temperatures from 25°C to 440°C, the Raman mode E(1TO) exhibits a soften behavior from 74cm~(-1) to 50 cm~(-1), whereas the mode B1+E keeps its frequency almost unchanged at 286 cm~(-1). It is also noticed that both frequency and damping constant of mode E(1TO) show rapid changing with temperature only when temperature beyond 380°C, blow the temperature they change very gradually. To explain the particular properties of the PT nanorods, the formation mechanism and an enhanced size effect have been discussed.