A polyethylene glycol-assisted route to synthesize Pb(Ni1/3Nb2/3)O3-PbTiO3 with improved electric properties

Polyethylene glycol (PEG)-assisted solid state reaction route is employed to prepare the relaxor-type ferroelectric powders and ceramics of (1-x)Pb(Ni1/3Nb2/3)O-3-xPbTiO(3) (PNN-PT) with the morphotropic phase boundary (MPB) composition at x=0.36 (0.64PNN-0.36PT). PEG additive with the molecular weight of 200 is introduced into PNN-PT oxide precursors in order to obtain the perovskite phase. The XRD and TG/DSC results demonstrate that the interactions between PbO and PEG favor the transformation from the lead-rich pyrochlore to the lead-deficient pyrochlore, thus facilitating the formation of the perovskite. Consequently, nearly pure perovskite 0.64PNN-0.36PT powders are synthesized at a relatively low temperature of 850 degrees C. A significant improvement of electric properties of the ceramics sintered at 1200 degrees C is achieved by PEG modification. The dielectric constant at room temperature and the maximum dielectric constant at T-c reach 4987 and 24307, respectively, at a frequency of 1 kHz. The piezoelectric constant d(33) is 460 pC/N.