Da Zhi Sun

Stabilization Effect in BaTiO3 Single Crystal during Aging below Tc

High purity BaTiO3 single crystal was aged below its Curie temperature for different times. The reverse transformation (from tetragonal to cubic) temperature was measured precisely by differential scanning calorimetry (DSC). It was observed that the reverse transformation temperature increased with increasing aging time, indicating ferroelectric phase became stable with aging. This behavior is the same as found in ferroelastic alloys. The origin of the stabilization effect in ferroelectric single crystals was discussed with respect to the distribution of point defects.

Preparation and Property of BaTiO3/PVDF Composites

Ferroelectric BaTiO3/polyvinylidene fluoride (BaTiO3/PVDF) composites were prepared by a coating technique. It was observed that BaTiO3 powders prepared with different thermal treatment temperatures affected dielectric performances of the composites. The polymer with fine BaTiO3 powder exhibited a lower dielectric loss than that with coarse powder. Fourier transform infrared spectrum was carried out to investigate the vibration of chemical bonds. The relationship between the dielectric property and intercoupling between F- ion and oxygen octahedron was discussed.

Fabrication and Electrical Properties of Grain-Oriented 0.91Pb(Zn1/3Nb2/3)O3– 0.09PbTiO3 Ceramics

(200) grain-oriented 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 (PMN–0.09PT) piezoelectric ceramics with a degree of orientation of 0.5052 have been produced from melt by a directional solidification method. The dielectric, ferroelectric, and piezoelectric properties were investigated, e.g., ε~4200, tanδ~0.8%, d33~2100pC/N, kt~58%, and k33~90%, some of these values are comparable to those of ~PZN–PT single crystals. The strain–electric-field curve with a maximum strain of 0.49% at a field of 7kV/cm and well-saturated hysteresis loops with a Pr~32 mC/cm2 were recorded. The results demonstrate that the directional solidification method is a promising technique to fabricate high performance grain-oriented PZN–PT ceramics.

Effects of La Doping on Microstructure and Ferroelectric Properties of BLTN Lead-Free Ceramics

Lead-free EO ceramics have been received increasing attentions from the view point of green environment in recent years. In this study, lead-free Ba6-1.5xLaxTi2Nb8O30 (0≤x≤7%) ceramics were synthesized by the conventional solid state reaction sintering method. The effects of lanthanum doping on the microstructure and electrical properties of Ba6Ti2Nb8O30 (BTN) ceramics were investigated and analyzed. The XRD results revealed that the lanthanum doping changed the BTN lattice parameters slightly. The sample grain size, dielectric constants (1kHz) and the temperature Tm gradually decreased with the increasing of lanthanum doped content. The optimized BLTN ceramic sample with x=4 mol % exhibited a good transparency and excellent electrical properties (Ps=6.41 μC/cm2, Pr=0.77 μC/cm2, and Ec=3.80 kV/cm).

Evidence of Normal to Anti Ferroelectric Phase Transition of PLZT Transparent Ceramics of Different Zr/Ti Ratio

The lanthanum-modified lead zirconate titanate transparent ceramics with different Zr/Ti ratio were prepared by the hot pressing sintering method. A single perovskive structure with a dense microsctructure was obtained and the transgranular fracture of PLZT ceramics tended to be more serious As the Zr/Ti ratio increases, the transmittance of PLZT ceramics tended to be higher and the transgranular fracture became more serious. The P-E loops changed froe a square hysteresis loop to a double tending slim hysteresis loop. Besides,the S-E loops changed from a approximate parabolic shape to a butterfly shape. These two loops confirm the transition from normal ferroelectric to anti ferroelectric phase occured with the Zr/Ti ratio increasing.

Study of Electrical and Aging Properties on the La-Doped Aurivillius Phase Ferroelectrics BaBi4Ti4O15

Aurivillius phase ferroelectrics Ba(Bi1−xLax)4Ti4O15(x=0-0.05) (BBiLxT) was synthesized by a modified high-temperature solid-phase route.The structure, the dielectric, the ferroelectric and the aging properties were investigated systematically. With the La3+ doping, the room temperature relative permittivity of the samples is increased, and dielectric loss is decreased. For the BBiLxT phase, only a weak variation with respect to the F2mm space group can be suggested from single crystal X-ray diffraction. The microstructure confirms the samples have a well-proportioned grain size and a higher density. The substitution also results in a marked improvement in the remnant polarization. The doping of La3+ in BBiLxT ceramics increased the room temperature relative permittivity aging properties.

Preparation and Characterization of BaBi2Nb2O9/PVDF Inorganic-Organic Composite Ultrafiltration Membranes

BaBi2Nb2O9/PVDF (polyvinylidene fluoride) composite ultrafiltration (UF)membranes were prepared by alloying BaBi2Nb2O9 (BBN) particles uniformly in the PVDF solution (15% polymer weight) and used a phase-inversion method. This paper studied the effect of the concentration of BBN from 0% to 5% in 0.2Mpa on pure water flux and rejection rate to Bovine serum albumin (BSA). The cross-sectional structures of composite membranes were observed by scanning electron microscopy (SEM). Moreover, XRD results revealed the crystal structure of PVDF. The experimental results showed that the BBN/PVDF composite ultrafiltration membranes were superior in separation performances than the pure PVDF membranes due to the addition of BBN.

Synthesis and Characterization of 3Y-TZP by Gel Solid-State Method

3Y-TZP powder has been successfully synthesized by gel solid-state method. The structural phases of powder particles were analyzed by X-ray diffraction and the morphology was analyzed by scanning electron microscopy. The average size of grains was 230 nm. The sintering behavior, mechanical properties and microstructure of 3Y-TZP ceramics sintered by this powder were investigated. The experiment results showed that the mechanical properties of ceramics were excellent.

Fabrication of 1-3 Type Multiferroic Nanostructured Composite Films by Chemical Methods

A new process was developed for fabrication of multiferroic 1-3 type nanostructured composite films. In this process, eletrodeposition method was adopted to prepare the arrays of cobalt nanowires as ferromagnetic composition. The images, phase structure and magnetic properties were characterized by SEM, XRD and VSM, respectively. The results showed that applying magnetic field during electrodepostion process could improve the alignment and height uniformity of nanowires arrays, inducing (002)-orientation growth. The PZT (53/47) precursor solution prepared for ferroelectric composition was infiltrated the spaces between nanowires. After annealed at 700 °C for 20 min, the 1-3 type multiferroic composite film was achieved. Preliminary results show this technique to have the potential to become a practical fabrication process for 1-3 type multiferroic composite films.

Preparation and Characterization of Ba0.6Sr0.4TiO3 Ceramics Doped with Al3+, Ga3+, and In3+

Ba0.6Sr0.4TiO3 materials doped with boron family Al3+, Ga3+ and In3+ are prepared by a ceramic process. The specimens possess condense microstructures. A low dielectric loss is achieved in the sample doped with In3+. Dielectric constants increase with decrease of the radii of doped ions. The results are discussed with respect to the interaction between oxygen ions and ions at B-site in ABO3 perovskite, which is revealed by Fourier transform infrared spectrum.