Pyrochlore-free Pb(Ni1/3Nb2/3)O3- PbTiO3 ceramics with superior piezoelectric properties synthesized using an optimized polyethylene glycol-assisted solid-state reaction

By introducing polyethylene glycol (PEG) into the raw oxide powders during ball milling, 0.64Pb(Ni1/3Nb2/3)O3-0. 36PbTiO3 (0.64PNN-0.36PT) powers, and ceramics with pure perovskite phase have been successfully synthesized. The effect of PEG on the formation of the perovskite phase was examined by varying the amount of PEG200 (40, 60, and 80 wt%) and using PEG with different molecular weight (Mw) during the ball-milling process. It was determined that interactions between PEG and PbO favor the formation of the desired perovskite phase. The dielectric constant and piezoelectric coefficient in samples prepared with 60 wt% PEG200 were found to be greatly enhanced as compared with that of samples synthesized by the conventional solid-state reaction method. The room temperature dielectric constant and the maximum dielectric constant (at Tm=90°C) reached 5950 and 33 680, respectively, at a measuring frequency of 1 kHz. The piezoelectric constant d33 reached an exceptionally high value of 570 pC/N. It was determined that PEG with a low Mw was more effective in the formation of the perovskite phase than those with a high Mw.