Hydrothermal Synthesis Of Lead Zirconate Titanate Based Piezoceramic Powders

PZT-based piezoceramics are widely used in many components including sensors, actuators and transducers. Therefore, the research of PZT-based piezoceramics with high performance has great significance. At the same time, the preperation process of powders is the important link. In this research, we tried to synthesize PZT and PLZT powders with high performance using hydrothermal method, and the major subject research and results are given as following:(1). We successfully synthesized PZT powders with single-phase, clean, cubic morphology and average size of 1μm using hydrothermal methods, and these powders are excellent for the sintering of PZT ceramic. Alkalinity has important influence on the solid solubility of Pb ion in A-site of PZT products. The higher the alkalinity reached, the more deficiency the Pb ion in A-site of PZT appeared. However, this kind of deficiency could be compensated by adding more Pb ion in the raw materials, and the higher the alkalinity reached, the more Pb ion we needed to add. Furthermore, the excessive Pb ions in the raw materials were not infinite at specified alkalinity. If the excessive Pb ions were too high, there would be a second phase appeared in the final products. Experiments proved that the best piezoelectric properties could be acquired when using PZT powders synthersized by hydrothermal methods at 200℃for 4 h from the alkalinity of 2M with excessive Pb ions of wt.80%. Concretely, the excellent properties are d33=225pC/N,kp=44.6%,Qm=305.4.(2). When we synthesize PLZT powders using one step hydrothermal method, the uniform mixing of reaction solutions has an important influence on the phase of the final products. The molecular uniform mixing of the raw materials helps PLZT crystalling phase appear, and appropriate adding of surfactant of CTAB restrainted the appearance of needle La(OH)3 phase. When the reaction condition is 200℃, 8 h and the CTAB concentration is 0.05 mol/L, we can abtain PLZT single phase. (3). In the experiments of Coprecipitation-assisted hydrothermal synthesis of PLZT, Tetragonal PLZT nano hollow nanospheres with uniform size of about 4nm have been successfully synthesized with reaction temperature of 200oC, reaction time of 24h and KOH concentration of 5M. The mineralizer KOH plays an important role in the composition and morphologic control of the PLZT nanoparticles. The PLZT products synthesized in the concentrated KOH consist of a large number of amorphous nuclei rapidly nucleated from concentrated monomers. On the contrary, relatively low concentration of KOH results in the formation of the amorphous coprecipitate particles that are able to simultaneously convert to PLZT crystalline particles. Thus, a moderate KOH concentration of 5 M results in the formation of highly crystalline PLZT hollow nanospheres. Moreover, the KOH concentration has little influence on the content of La, Zr and Ti in the final PLZT particles except for Pb since the lead vacancies in A-site are easily formed under concentrated KOH conditions.The authors would like to thank the support of the National Nature Science Foundation of China (No. 50872053) and the Cultivation Fund of the Key Scientific and Technical Innovation Project of Ministry of Education of China (No.707031) and the New Century Excellent Researcher Award Program from Ministry of Education of China (No. 707031).