Key Engineering Materials Vols. 336-338

Abstract: The radio frequency (RF) sputtering method was utilized to grow PZT-based ferroelectric thin films with the chemical composition Pb(Zr0.53Ti0.45W0.01Cd0.01O3). The thin films were characterized in terms of their microstructure, crystalline structure, chemical composition and dielectric properties. The processing conditions diagram was defined, which ensured conservation of stoichiometry of the chemical composition of the thin films. Complex impedance spectroscopy was used to measure frequencydependent dielectric properties of the PZT-type thin films. Great application potential of the PZT-based thin films was considered and possibility to employ as-obtained PZT thin films as active elements of the piezoelectric sensors was reported.

Abstract: The influences of the substitution of (Zn1/3Nb2/3) group for Ti as well as addition of Fe2O3 and K2CO3 on d33, kp, εr, and tgδ of the Pb[Zr0.46Ti0.54-x(Zn1/3Nb2/3)x]O3 + y mol%Fe2O3+z mol%K2CO3 (PZNPZT) (0 ≤ x ≤ 0.20, 0 ≤ y ≤ 0.10, 0 ≤ z ≤ 0.20) ceramics were investigated. The experimental results demonstrated that when x increases in Pb[Zr0.46Ti0.54-x(Zn1/3Nb2/3)x]O3+0.3 mol%Fe2O3+0.5mol%K2CO3 ceramics, the d33, kp, εr, and tgδ increase and approach to their maximum values, then eventually decrease. XRD analysis revealed that the perovskite structure of the materials transfers from tetragonal phase to rhombohedral phase. The relative dielectric constant (εr) decreases dramatically in the rhombohedral phase area near the MPB; the d33 and εr decrease with the small amount of added Fe2O3 and K2CO3, which also contributes to densification of the PZN-PZT ceramics. The optimized piezoelectric performances through the experiment were obtained as d33=280 pC/N, kp=0.62, εr=900, tgδ=0.003.

Abstract: Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) solid solutions with composition near the morphotropic phase boundary (MPB) (33mol% PT) were successfully synthesized by the molten salt synthesis (MSS) method at 800°C for 30min using Li2SO4-Na2SO4 and NaCl-KCl molten salts as a medium of reaction, respectively. The influences of processing parameters, such as temperature, time, and type of salts, on the formation and the micrographs characteristics of the PMN-PT powders were discussion. It was found that the PMN-PT powder obtained by the MSS method has a relatively uniform size distribution and a better dispersivity of particle, and an average size of PMN-PT particles with smooth surface was around 0.3∼0.5 μm. With other conditions being kept same, chloride molten salt is more propitious to the formation of PMN- PT solid solutions, and improving the compositional homogeneity of PMN-PT powders.

Abstract: Ferroelectric ceramics of (1
x)(0.8PMN
0.2PNN)
xPT (x = 0.28
0.43) were synthesized by the columbite precursor method. Their phase structures as well as the dielectric, ferroelectric and piezoelectric properties were investigated. X-ray diffraction (XRD) results demonstrate that the morphotropic phase boundary (MPB) of this system lies in the composition range of x = 0.31–0.37. Examination of the dielectric behavior indicates that the ceramics exhibit high dielectric constants near the MPB compositions. In addition, the piezoelectric properties of the ceramics were found quite well around the MPB. The interrelated mechanism was also discussed.

Abstract: The Pb(Zr0.52Ti0.48)O3 thin films with 0-2at.%Gd dopants (denoted as PGZT) were prepared on Pt/Ti/SiO2/Si substrates by a sol-gel technique and a rapid thermal annealing process. The structures of PGZT films were characterized and the ferroelectric properties such as P–V loop, C–V and I–V characteristics were investigated. Improved polarization (2Pr = 46.373 μC/cm2) and the low leakage current (J = 1.5×10-9 A/cm2 at the electric field of 400 kV/cm) were obtained in the PZT thin film with 1at.% Gd dopant, which was better than that of the pure PZT thin film (2Pr = 39.099 μC/cm2, J = 4.3×10-8A/cm2). With the Gd contents up to 2at.%, a decreased remanent polarization was found.

Abstract: <001> textured Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (PMN-32.5PT) ceramics were prepared by reactive templated grain growth (RTGG). Plate-liked {001}-SrTiO3 single crystal particles were used as template seeds. MgNb2O6, TiO2, PbO were mixed with SrTiO3 templates as a reactive matrix. SrTiO3 templates were oriented after tape-casting. The textured PMN–32.5PT ceramics were produced after heat treatment. In preparing textured PMN-32.5PT, RTGG was more efficient than TGG because of the chemical energy released in reaction. The final texture degree was very sensitive to the sintering history. An initial anneal step below the melting point of PbO resulted in better development of texture.

Abstract: 0.85Pb(Zn1/3Nb2/3)O3-0.10BaTiO3-0.05PbTiO3 (abbreviated as PZN-based ceramics hereafter) ternary system ceramics with Zn2+ deficiency were synthesized by the columbite method. The effect of deficient Zn2+ on phase structure, ordered micro-region size and dielectric properties was investigated in detail. The analysis of Raman scattering spectra demonstrated that Zn2+ deficiency sharply enlarged the ordered micro-region size. Zn2+ deficiency significantly increased the dielectric constant, and decreased the diffusion degree of phase transition. There is a close correlation between effective ordered micro-regions size and dielectric properties for the PZN-based ceramics.

Abstract: Ceramics with the type of 0.50Pb(Ni1/3Nb2/3)O3-0.15PbZrO3-0.35PbTiO3 were synthesized by conventional mixed-oxide technique. The dielectric and ferroelectric properties of this composition were investigated in detail. Frequency dispersion and diffuse phase transition were observed in the dielectric behaviors. The revealed electrical properties are εm = 22388, Pr = 21.449 μC/cm2 and Ec = 5.191 kV/cm. XRD experiments demonstrate that this composition is within the MPB region, which may help to explain the super electrical properties discussed in this study.

Abstract: A small piece of <110> orientated relaxor-based ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystals was embedded in Pb(Mg1/3Nb2/3)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3 (PMN-PNN-PT) polycrystalline matrix to form the fully dense disk by spark plasma sintering (SPS) technique. Specimens were subsequently annealed to promote the boundary migration of the template single-crystal through a process termed as solid-state single crystal growth. It was found that the addition of excess 5 wt% PbO can promote the crystal growth, and the 2D morphology with V-shaped single crystals of PMN-PNN-PT were also observed. The possible growth mechanism was discussed.