Phase transition, structural and electrical properties of Pb(Zn1/3Nb2/3)O3-doped Pb(Ni1/3Nb2/3)O3–PbTiO3 ceramics prepared by solid-state reaction method

Phase pure perovskite (1−x−y)Pb(Ni1/3Nb2/3)O3–xPb(Zn1/3Nb2/3)O3–yPbTiO3 (PNN–PZN–PT) ferroelectric ceramics were prepared by conventional solid-state reaction method via a B-site oxide mixing route. The PNN–PZN–PT ceramics sintered at the optimized condition of 1185 °C for 2 h exhibit high relative density and rather homogenous microstructure. With the increase of PbTiO3 (PT) content, crystal structure and electrical properties of the synthesized PNN–PZN–PT ceramics exhibit successive phase transformation. A morphotropic phase boundary (MPB) is supposed to form in (0.9−x)PNN–0.1PZN–xPT at a region of x=32–36 mol% confirmed by X-ray diffraction (XRD) measurement and dielectric measurement. The MPB composition can be pictured as providing a “bridge” connecting rhombohedral ferroelectric (FE) phase and tetragonal one since crystal structure of the MPB composition is similar to both the rhombohedral and tetragonal lattices. Dielectric response of the sintered PNN–PZN–PT ceramics also exhibits successive phase-transition character. 0.64PNN–0.1PZN–0.26PT exhibits broad, diffused and frequency dependent dielectric peaks indicating a character of diffused FE–paraelectric (PE) phase transition of relaxor ferroelectrics and 0.40PNN–0.1PZN–0.50PT exhibits narrow, sharp and frequency independent dielectric peaks indicating a character of first-order FE–PE phase transition of normal ferroelectrics. The FE–PE phase transition of 0.56PNN–0.1PZN–0.34PT is nearly first-order with some diffused character, which also exhibits the largest value of piezoelectric constant d33 of 462pC/N.