Ke Pi Chen

Structure and Piezoelectric Properties of PZN-PNN-PT Ceramics

(1-x)(0.64PNN-0.36PT)-x(0.91PZN-0.09PT) ferroelectric ceramics with different x were synthesized by the columbite precursor method. The phase structure and piezoelectric properties were investigated. XRD profiles implied that with the increasing of x, samples could no longer maintain the pure perovskite phase. All the compositions were found to lie within the region of the morphotropic phase boundaries (MPBs) with different contents of rhombohedral and tetragonal phases. The piezoelectric coefficients for compositions with x £ 0.30 were obviously better than those for the rest ones and the composition with x = 0.15 exhibited the largest value of d33 among all the samples. The relationship between the structure and the piezoelectric properties was discussed.

Molten Salt Synthesis of CaCu3Ti4O12

CCTO powders were prepared by using molten salt method in the NaCl-KCl system. The effects of temperature and holding time on phase compositions, particle morphology and size have been investigated by X-ray diffraction, scanning electron microscope and laser particle size analyzer. Using CaCO3, CuO and TiO2 as starting materials, CCTO compound could be synthesized at any temperature from 800oC to 1000oC in the NaCl-KCl system. The average particle size increased obviously with the increasing of temperature above 850 oC. Holding time had great effect on grain size and morphology.

Dielectric Properties of Zr-Doped CaCu3Ti4O12 Ceramics

CaCu3(Ti1-xZrx)O12 ceramics (x = 0.02, 0.04, 0.06, 0.08) were prepared by the conventional solid-state reaction method. Phase compositions, microstructure and dielectric properties were examined by XRD, SEM and impedance spectroscopy, respectively. The experimental results indicated that there is no obvious effect on microstructure characteristic by substituting Zr4+ for Ti4+. It was found that the values of the dielectric constant for all of the samples dropped into the order of 102, which is significantly lower than the order of 105 that of normally reported in the literature. It was suggested that the presence of impurity phases played an important role for the degeneracy of dielectric properties.

Pb(Mg1/3Nb2/3)O3- Pb(Ni1/3Nb2/3)O3-PbTiO3 Crystals by Solid State Growth

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.

Textured Pb(Mg1/3Nb2/3)O3-PbTiO3 Ceramics by Templated Grain Growth

Fiber textured 0.70PMN-0.30PT ceramics was fabricated using the Templated Grain Growth (TGG) process. Tabular SrTiO3 particles synthesized in molten NaCl-KCl salts were used as templates and oriented in fine 0.70PMN-0.30PT matrix during rolling. Tabular SrTiO3 particles can stabilize in sintering by SPS technique and annealing. A degree of [001] texture (Lotgering factor ~ 0.38) was obtained by heteroepitaxial growth of oriented single PMN-PT on the SrTiO3 template particles.