Kepi Chen

Morphotropic phase boundary and electrical properties of K1−xNaxNbO3 lead-free ceramics

Lead-free K{sub 1-x}Na{sub x}NbO{sub 3} ceramics with x=0.48-0.54 were prepared by a conventional solid-state reaction method to investigate the influence of the K/Na ratio on phase structures and electrical properties. The results suggest that a typical morphotropic phase boundary exists at x=0.52-0.525, separating the monoclinic and orthorhombic phases. The sample with the composition near x=0.52 shows the maximum values of the piezoelectric constant (d{sub 33}=160 pC/N) and the electromechanical coupling coefficient (k{sub t}=47%). The results provide a helpful guidance to consider the optimal ratio of K to Na for designing and developing new (K,Na)NbO{sub 3}-based ceramics.Lead-free K1−xNaxNbO3 ceramics with x=0.48–0.54 were prepared by a conventional solid-state reaction method to investigate the influence of the K/Na ratio on phase structures and electrical properties. The results suggest that a typical morphotropic phase boundary exists at x=0.52–0.525, separating the monoclinic and orthorhombic phases. The sample with the composition near x=0.52 shows the maximum values of the piezoelectric constant (d33=160 pC/N) and the electromechanical coupling coefficient (kt=47%). The results provide a helpful guidance to consider the optimal ratio of K to Na for designing and developing new (K,Na)NbO3-based ceramics.

Study of the structure and dielectric relaxation behavior of Pb(Ni1/3Nb2/3)–PbTiO3 ferroelectric ceramics

Abstract Relaxor-type ferroelectric ceramics, (1−x)Pb(Ni1/3Nb2/3)O3–xPbTiO3 (x=0.28–0.42) were synthesized by the columbite precursor method. The phase structure and dielectric properties were investigated. X-ray diffraction results demonstrate that a region with both pseudocubic and tetragonal phase in existence lies in the composition range x=0.34–0.38, which is the morphotropic phase boundary (MPB). Examination of the dielectric behavior indicates that the ceramics exhibit abnormal high dielectric constant near the MPB composition. In addition, the transformation of (1−x)PNN–xPT from relaxor to normal ferroelectric behavior with the PT content increasing is successive.

Dielectric and ferroelectric properties of Pb(Ni1/3Nb2/3)O3–PbTiO3 ferroelectic ceramic near the morphotropic phase boundary

Abstract (1−x)Pb(Ni1/3Nb2/3)O3–xPbTiO3 (x=0.28–0.42) system ferroelectric ceramics were synthesized by the columbite precursor method. The phase structure and dielecric, ferroelectric properties were investigated. X-ray diffraction (XRD) results demonstrate that the morphotrophic phase boundary (MPB) lies in the composition range x=0.34–0.38. Examination of the dielectric behavior indicates that the ceramics exhibited very high dielectric constant near the MPB composition. In addition, the ferroelectric properties of the ceramics were found also quite well around the MPB.

Microstructure and electrical properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ceramics by spark plasma sintering

Abstract 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramics were synthesized by Spark Plasma Sintering (SPS) technique. The phase compositions, microstructure and electrical properties were investigated. The results indicated that this technique was an alternative sintering technology to synthesize dense lead-based relaxor ferroelectric ceramics at rather low temperature and in a short time.

Morphotropic phase boundary in Pb(Ni1/3Nb2/3)O3–PbTiO3 solid solution system

Abstract (1− x )Pb(Ni 1/3 Nb 2/3 )O 3 – x PbTiO 3 ( x =0.28–0.42) solid solution was synthesized by a B-site precursor method and characterized by high-resolution synchrotron radiation X-rays diffraction and dielectric measurement. The results indicated that composition induced phase transition is not continuous, and the intermediate monoclinic phase may exist in morphotropic phase boundary between rhombohedral and tetragonal phases in this solid solution system.