Qing Rui Yin

Electrical Properties of the Mixed Bismuth Layer-Structured Bi7Ti4NbO21 Ceramics

A mixed bismuth layer-structured compound, Bi7Ti4NbO21, has been prepared by the conventional solid state reaction. It showed an orthorhombic symmetry with a = 5.4428, b = 5.4043 and c = 29.041 Å by X-ray powder diffraction analysis. The hysteresis loops as a function of temperature were observed with a standardized ferroelectric test system. The remanent polarization and the coercive field of the material at 140°C were 14.06 µC/cm2 and 78.6 kV/cm, respectively. Thermal dependence of dielectric permittivity showed two-phase transitions at around 670°C and 845°C, which were also investigated by TSC and DSC. Finally, piezoelectric properties were obtained with a piezoelectric coefficient d33 = 10 pC/N. It was observed that Bi7Ti4NbO21 underwent a ferroelectric–paraelectric phase transition at 845°C by depolarization experiments.

Study on Ferroelectric and Dielectric Properties of Zr-Doped Sr2Bi4Ti5O18 Ceramics

Zr-doped Sr2Bi4Ti5O18 (SBTi) bismuth layer-structured ferroelectric ceramics were prepared and studied. XRD patterns revealed that all the ceramic samples were single phase compounds. SEM images showed that dense microstructures with uniform gain size were obtained in all samples. The effects of Zr4+ doping on the dielectric, ferroelectric and piezoelectric properties of SBTi ceramics were also investigated. It was found that Zr4+ dopant gradually decreased the Curie temperature (Tc), enhanced the remnant polarization (2Pr) and decreased the coercive field (Ec) of SBTi ceramics. Furthermore, the piezoelectric properties of the SBTi ceramics were improved by enlarging the content of Zr. The SBTi ceramics with 4 mol% of Zr4+ dopant exhibited good electrical properties: d33 = 21 pC/N, 2Pr = 14.3 μC/cm2, Tc = 251°C, εr = 376, tanδ = 1.8%.

Effects of Donor Doping on Microstructure and Electrical Properties of Bismuth Layer-Structured Bi4Ti3O12 Ceramics

A study was conducted on the effects of donor dopants, Nb2O5 and WO3, on microstructure and electric properties of Bi4Ti3O12 (BIT) ceramics. X-ray diffraction patterns of the materials showed a single orthorhombic phase structure. The microstructure results revealed the appearance of plate-like grain. The donor doping decreased the conductivity of BIT by as much as 3 orders of magnitude. The dielectric and ferroelectric properties of doped-BIT materials were also investigated. The decrease in the electrical conductivity allowed the doped samples to be poled to develop piezoelectricity. Thermal annealing studies of the samples indicated the donor-doped BIT were suitable candidate materials for high-temperature piezoelectric applications.

Microstructure and Mechanical Properties of PMS-PZT Ceramics with Silica Additives

The use of lead zirconate titanate ceramics for high power application must have superior mechanical properties, the composition Pb0.98Sr0.02(Mn1/3Sb2/3)0.05Zro.48Ti0.47O3 + x wt% SiO2 (x = 0-1.0) have been studied for this purpose. The microstructures were observed to study the improvement of mechanical properties by SEM and TEM. The nano-scale secondary phase of SiO2 and PbSiO3 were observed on the grain boundary and the twinned ZrO2 was found surrounded by PMS-PZT perovskite phase. The mechanism to the occurrence of twinned ZrO2 and its content increased with increasing Si concentration are discussed in the paper. The occurrence of the nonferroelectric phase such as ZrO2, SiO2 and PbSiO3 on the grain boundary should be the main reason for great improvement of fracture strength.

The Influence and Mechanism of the Electrical Conductivity of (Ca,Sr)Bi4Ti4O15 Piezoelectric Ceramics by Doping of CeO2

In this paper, the bismuth-layered structure piezoelectric ceramics (Ca,Sr)Bi4Ti4O15 doped with CeO2 are prepared by the solid state reaction method. The crystal structure of the ceramics is determined by X-ray diffraction and the single orthorhombic structure phase is found. However, the doping of CeO2 increase the lattice parameters a, b, c. As a result, the ions of Ce enter into the lattice of the bismuth-layered structure and occupy A sites in the perovskite layer of bismuthlayered structure lattice. The temperature dependence of the conductivity shows that the resistivity increases by doping of CeO2 and reaches its maximum when the doping content is 0.4mol%. The mechanism of the CeO2 doping is also analyzed. By the investigation of XPS, the Ce ions have two types of valences: Ce3+ and Ce4+. The existence of Ce ions strengthened the weak Bi-O bonding and decreased the oxygen vacancies in the lattice, so the ceramics have lower conductivity.

Effects of SiO2 Substitution on Piezoelectric and Mechanical Properties of PMS-PZT Ternary Piezoelectric Ceramics

The effects of SiO2 additives on microstructure, piezoelectric and mechanical properties were investigated for Pb0.98Sr0.02(Mn1/3Sb2/3)0.05Zro.48Ti0.47O3 (PMS-PZT) ternary system close to the morphotropic phase boundary. Piezoelectric coefficient (d33) and electromechanical coupling factor (Kp) considerably deteriorated with the substitution of SiO2 increased. On the other hand, the mechanical quality factor (Qm) increased, the maximum value was 1800. Fracture strength of 1.0 wt% SiO2 added the specimens reached to 106.54 MPa which was about 1.4 times higher than pure PMS-PZT ceramic. The rapid improvement of fracture strength probably due to the decrease of grain size, pore distribute and the second phase (redundant Si4+ ions) segregating on the grain boundary which enhanced the bond energy of grain boundary. The optimized concentration of SiO2 doped PMS-PZT ceramics was 0.4 wt% for high power application: d33 = 300 PC/N, Kp = 0.51, Qm = 1500, tand = 0.32% and the fracture strength was 88.5MPa.

Influence of Dy Doping on Microstructure of PLZT Ceramics

Polycrystalline dysprosium (Dy) doped PLZT ceramics with compositional formula [Pb0.88 (La1-xDyx)0.12](Zr0.40 Ti0.60)O3] were prepared by hot-pressed solid-state method. Dy3+ concentration x varied from 0 to 0.5. All samples present single phase with tetragonal structure and the tetragonality was increased with increasing Dy3+ content. The Raman spectra indicated that Dy3+ ions could be distributed in both A and B site of ABO3 perovskite structure depending on the doping amounts.

Effect of Nickel Doping on Dielectric, Piezoelectric Properties and Domain Configurations of PZT Based Ceramics

The aims of present study were investigated the effect of nickel doping on the dielectric and piezoelectric properties of P(BN)ZT solid solution. P(BN)ZT powder doped with nickel nanoparticle in the composition of (1-x) PBNZT–xNi when x = 0, 2, 4, 6, 8 and 10 percent by mole. P(BN)ZT doped with nickel powder were calcined at 900 °C for 2 h and sintered at the temperature range of 1150 -1250°C for 2 h with heating/cooling rate of 5 °C/min. The dielectric constant (er) and the dielectric loss tangent (tand) of all ceramics were measured at room temperature using LCR meter. The piezoelectric properties (d33) were measured at room temperature using d33 meter. The micro and nano-domain structure was clearly observed by piezo-response force microscopy (PFM). From the results, it can be seen that the dielectric and piezoelectric decreased with increasing Ni particle of all composition (0.0-0.1 mol%). Moreover, PFM images show that the micro (180°) and nano (90°) domain are orientated at the surface region in submicron-scale of P(BN)ZT ceramics with doped nickel nanoparticle.

Ferroelectric and Dielectric Properties of Vanadium-Doped Bismuth Layer Sr2Bi4Ti5O18 Ceramics

Sr2Bi (4-x/3) Ti (5-x) VxO18 (x = 0.0-0.06) (SBTV) ceramics were prepared by a solid-state reaction method, and the ferroelectric and dielectric properties of the ceramics were investigated with respect to the amount of V deficiency. XRD analysis indicated that the oxide compounds were Aurivillius phases. The Curie temperature of SBTV ceramics was improved by doping of certain amount of V. The V deficiency also led to a steady increase in the density together with a decrease in the coercive field. For the ceramics with x = 0.06, the properties become optimum: d33 = 19 pC/N, Tc = 306oC, Ec = 43.7 KV/cm.

Preparation and Dielectric Properties of the Layered Perovskite Sr4Bi4Ti7O24 Ferroelectric Ceramics

Sr4Bi4Ti7O24 (SBT7) ceramics were prepared. X-ray powder diffraction indicated that single layered perovskite ferroelectrics were obtained. The ferroelectric and dielectric properties of SBT7 ceramics were investigated. The results showed that Sr4Bi4Ti7O24 is piezoelectric material. The dielectric properties were measured as a function of temperature and two peaks were observed in the curve.