High-Performance Ceramics V

Abstract: The measurement of temperature based on the characteristic lifetime decay in luminescence intensity of dopant ions following excitation is described with illustrations drawn from europium doping in yttria-stabilized zirconia. The method is particularly attractive for making measurements in a temperature gradient, such as those in thermal barrier coatings.

Abstract: Synthesis of Zn-doped PbTiO3 was done using solid-state method. The effects of varying amount of Zn were investigated. Stoichiometric amount of precursors were mixed and ground. The pressed mixtures were calcined at 800°C and sintered at 1,100 °C after regrinding. The samples were characterized using X-ray Diffraction (XRD), Differential Thermal Analysis (DTA), and Scanning Electron Microscopy (SEM). The XRD verifies the existence of PTO in the samples. DTA shows the thermal profile of the samples. Among the different concentrations of Zn that were added, the sample with 5% mole fraction showed the lowest melting point. For 5% mole fraction and greater, SEM images showed flattening and fusing of grains.

Abstract: High-performance fine-grain (1-x)BiScO3-xPbTiO3 ceramics were prepared by two-step sintering method. Influences of sintering temperature, holding time, and composition on the microstructure and properties were discussed. The BSPT ceramics obtained via two-step sintering reaches density higher than 95% at a low temperature of 800°C without any sintering aid, and the grain size of the ceramics is also effectively controlled. Excellent piezoelectric properties between the composition of x=0.63 and x=0.64 reveals a probable MPB in this range, suggesting a potential approach to pursue high performance BSPT ceramics.

Abstract: In this study PZT-green fibres containing 50, 54 and 58 vol.% PZT powder were extruded. The influences on the mixing torque, the apparent shear rate and the extrudability were investigated and a theoretical maximum powder loading content was calculated using a model introduced by Frankel and Acrivos. The influence of powder loading content on the microstructure (porosity and grain size), the phase composition and on the final ferroelectric properties of sintered PZT fibres was investigated. The measurements revealed that the production of PZT fibres with homogeneous properties requires a minimum powder loading content of 58 vol.% PZT powder.

Abstract: <001> textured 0.675Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 (PMN-32.5PT) ceramics were prepared by templated grain growth with micron scale BaTiO3 platelet templates. 0%~7% excess PbO was added to form liquid phase. The influence of liquid phase concentration on the growth of matrix and templated grains was investigated. The growth process was controlled by a dissolution-precipitation mechanism. The templated grain growth was accelerated by the formed liquid phase and resulted in highly textured PMN-32.5PT ceramics.

Abstract: In the frame of shock-induced depoling, PZT 95/5 ferroelectric ceramics with niobium doped has been assembled for the pulsed power supply, and the electrical current output has been investigated under the action of shock wave in a "normal mode". The electrical response of LRC load especially for the small resistance (R) and small inductance (L) load was studied. Plane-shock-wave tests were conducted, and the PZT 95/5 ceramics stacked in parallel were devised to generate high-power electrical pulse. An output current of 7 kA has been obtained, and the corresponding rise time of the front edge is under 500 ns. Theoretical calculations were conducted and a good agreement with the experiment presented.

Abstract: Electric power of hundreds of kilowatts can be produced in a few microseconds by sudden release of bound charge on the surface of ferroelectric ceramic through shock wave compression. In order to understand the depolarization process, knowledge of the discharge behavior of ferroelectric ceramic under shock wave compression is essential. Gas-gun facility has been used to investigate the shock-induced depolarization kinetics of tin-modified lead zirconate titanate ferroelectric ceramic. Experiments were conducted in the normal mode in which the shock propagation vector was perpendicular to the remanent polarization. Two kinds of specimens with the ferroelectric-toantiferroelectric transformation hydraulic pressure respectively at 80 MPa and 180 MPa were tested. The output currents as a function of load resistance were measured. A computation model was developed to describe the electrical behavior of PSZT ceramic under shock wave compression, which adequately explained the observed experimental results.

Abstract: Lead magnesium niobate-lead titanate (0.8Pb(Mg1/3Nb2/3)O3-0.2PbTiO3, PMN-PT) thick films in the thickness range about 75 μm have been successfully fabricated on Au-coated Al2O3 substrates by electrophoretic deposition (EPD). Non-aqueous colloidal suspensions suitable for EPD were prepared by mixing ultrasonically PMN-PT particles in ethanol with pH=6.0. The effect of EPD process parameters such as deposition voltage, deposition time and the specific deposition mass of PMN-PT particles were investigated. The EPD parameters were optimized in order to obtain crack-free, high-quality uniform ceramic films. The deposited pyrochlore-free PMN-PT thick films were sintered at 1000oC for 30 min, and the phase evolvement and the microstructure of the film were characterized by X-ray diffraction and scanning electron microscope.