Papers by Author: Yong Ke Yan

Abstract: A lead-free piezoelectric ceramic binary system based on bismuth sodium titanate (Bi0.5Na0.5)TiO3 (BNT)-bismuth potassium titanate (Bi0.5K0.5)TiO3 (BKT) was synthesized by conventional mixed-oxide technique. The XRD analysis showed that the rhombohedral-tetragonal morphotropic phase boundary (MPB) of the Bi0.5 (Na1-xKx)0.5 TiO3 system was in the composition range of x = 0.16 ~ 0.20. In addition, the piezoelectric properties of this system were also investigated. It was indicated that the piezoelectric properties are better with the compositions near the rhombohedral phase within the MPB than the compositions near the tetragonal phase.

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: High <001>-textured Na1/2Bi1/2TiO3-BaTiO3 (6mol%BaTiO3) ceramics were fabricated by reactive-templated grain growth (RTGG), using plate-like Bi4Ti3O14 particles prepared by a molten salt method as the templates. The effect of template concentration on the texture development and microstructure evolution was studied, and the mechanisms of grain orientation and densification were also discussed. The design of Bi element reaction has important impact on the texture development.

Abstract: Lead-free Na1/2Bi1/2TiO3-6BaTiO3 (BNT-6BT) ceramics with different dopants were prepared by a conventional ceramic fabrication technique. The influence of doping CeO2, La2O3, Nb2O5 and Co2O3 on the structure was studied, and the mechanism of soft and hard additives with A-site or B-site substitute changing the piezoelectric properties was discussed. It was found that the rhombohedral-tetragonal morphotropic phase boundary (MPB) of the Na1/2Bi1/2TiO3-6BaTiO3 was not changed obviously.

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.