Preparation and electrical properties of high-Curie temperature ferroelectrics

(1-x)Pb(Fe(0.5)Nb(0.5))O(3- x)Pb(Zr(0.2)Ti(0.8))O(3) (PFN-PZT, x = 0.75, 0.80, 0.85) ferroelectric ceramics were prepared by conventional solid-state reaction method via the wolframite precursor route. XRD measurements confirmed that the synthesized PFN-PZT ceramics are of pure tetragonal perovskite structure. With the increase of Pb(Zr(0.2)Ti(0.8))O(3) (PZT) content, tetragonality (defined as the ratio of cell parameter c/a) increases slightly accompanied by the variation of cell volume. At the optimized sintering condition of 1175 degrees C for 2 h, the 0.20PFN-0.80PZT ceramics exhibit the largest value of relative density (93.77%). The PFN-PZT ceramics exhibit first-order ferroelectric phase transition of typical normal ferroelectrics, where the dielectric response peaks are narrow, sharp and without frequency dispersion, and the dielectric constant above Curie temperature (T(C)) can be fitted well by Curie law. The sintered PFN-PZT ceramics exhibit high-T(C), and with the increase of PZT content, T(C) increases and reaches 368, 394 and 401 degrees C, respectively. With the increase of PZT content, the P-E ferroelectric hysteresis loops of the PFN-PZT ceramics become narrower accompanied by the decrease of remanent polarization (P(r)) and coercive field (E(C)). Piezoelectric constant d(33) of all the PFN-PZT ceramics is small, less than 10 pC/N.