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Abstract: Oxide-doped PbFe1/4Sc1/4Nb1/2O3 (PFSN) ceramics were prepared by the conventional ceramic processing via a B-site oxide mixing route. The oxide-doped PFSN ceramics exhibit pure rhombohedral perovskite structure and high relative density. Due to the MnO2 and Li2CO3 doping, the synthesized ceramics exhibit improved dielectric property, and excellent ferroelectric and piezoelectric properties, which can be attributed to a charge compensation mechanism where donor defects are generated by different ionization paths. The values of remnant polarization P r , electromechanical coupling coefficient K p and piezoelectric constant d 33 of the MnO2- and Li2CO3-doped PFSN ceramics are 16.35μC/cm2, 0.232 and 112.7pC/N, and 29.22μC/cm2, 0.241 and 112.5pC/N, respectively. Therefore, oxide doping is an efficient method to improve dielectric, ferroelectric and piezoelectric properties of the PFSN-based ferroelectric ceramics. [Copyright &y& Elsevier]

Abstract: The ternary system of 0.56Pb(Ni1/3Nb2/3)O3–0.10Pb(Zn1/3Nb2/3)O3–0.34PbTiO3 (0.56PNN–0.10PZN–0.34PT) ceramics were prepared by conventional solid-state reaction method via straight mixed oxide method, columbite precursor method and B-site oxide mixing route. X-ray diffraction (XRD) measurement demonstrated that both the tetragonal and rhombohedral phases coexist in the B-site oxide mixing route prepared ceramics accompanied by the largest content of perovskite phase of 95.18%. The 0.56PNN–0.10PZN–0.34PT ceramics prepared by the straight mixed oxide method and the B-site oxide mixing route exhibit rather homogeneous microstructure. As a comparison, in the columbite precursor method prepared ceramics nebulous granules and octahedral or other polyhedral morphology grains are observed. All the sintered ceramics exhibit diffused ferroelectric phase transition where the dielectric response peaks are broad, diffused and strongly frequency dependent. However, the temperature of dielectric maximum (T m) increases greatly from 398.0K of the 0.56PNN–0.10PZN–0.34PT ceramics prepared by the B-site oxide mixing route to 423.3K of the ones prepared by the straight mixed oxide method. Saturated and symmetric P–E hysteresis loops are observed in all the sintered ceramics, where the B-site oxide mixing route prepared ceramics exhibit large value of remanent polarization (P r) of 17.13μC/cm2 and the least value of coercive field (E c) of 11.99kV/cm. Piezoelectric constant (d 33) exhibits the largest value of 449pC/N for the ceramics prepared by the B-site oxide mixing route. Such results are related to the phase composition, density and porosity of the ceramics. [Copyright &y& Elsevier]

The dielectric and piezoelectric properties of 0.62Pb(Mg1/3Nb2/3)O3–0.38PbTiO3 single crystal (PMNT62/38) were investigated in this work. Power X-ray diffraction demonstrated PMNT62/38 had a tetragonal structure at room temperature. The Curie temperature was 187 °C on heating. The poled and as-grown dielectric constants ϵr of [001] oriented PMNT62/38 at room temperature were ∼500 and ∼5000, respectively. The remanent polarization Pr and coercive field Ec for [001] oriented one were 34.2 μC/cm2 and 8.25 kV/cm, respectively. The strain at 15 kV/cm and −15k V/cm were 0.078 and 0.125%, respectively. The piezoelectric constant d33 was ∼350 pC/N. The electromechanical coupling coefficients; 0.89 of k33, 0.61 of kt, 0.46 of k31 and 0.45 of k15 were calculated from measured resonance and anti-resonance frequencies by impedance resonance techniques. In single domain process it was found the re-oriented domains of [001] poled PMNT62/38 were instable, which caused it hard to align the spontaneous polarizations to create a single domain crystal. [Copyright &y& Elsevier]

Abstract: 1wt% Li2CO3- or La2O3-doped 0.75BaTiO3–0.15CaTiO3–0.1BaZrO3 (BCZT) lead-free ceramics were prepared by the solid-state reaction method sintered at 1480–1520°C for 2h. Sintering temperature, oxide doping and poling electric field influence crystal structure and electrical properties of the sintered BCZT ceramics. Due to oxide doping the BCZT ceramics exhibit pure perovskite structure sintered in a rather wide sintering temperatures with composition locating at the rhombohedral side around the morphotropic phase boundary. The oxide-doped BCZT ceramics exhibit rather homogeneous microstructure morphology, in which grain size of the Li2CO3-doped BCZT ceramics and La2O3-doped BCZT ceramics is around nm-scale and in μm-scale, respectively. Li2CO3 doping increases the value of dielectric constant maximum (ε m ), sharpens the dielectric response peaks and suppresses the dielectric frequency dispersion of the BCZT ceramics, whereas the temperature of ε m (T C /T m ) changes negligibly. As comparison, La2O3 doping decreases the T m temperature and enhances dielectric frequency dispersion greatly. The Li2CO3-doped BCZT ceramics exhibit similar P–E hysteresis loop to that of the undoped BCZT ceramics, whereas La2O3 doping deteriorates ferroelectric property apparently. Li2CO3 doping improves piezoelectric property whereas La2O3 doping deteriorates piezoelectric property of the BCZT ceramics, which can be interpreted by the formation of different point-charge defects induced by oxide doping. [Copyright &y& Elsevier]