Study On Preparation And Properties Of PMN-PFN-PFW Electrostrictive Materials

0.2Pb(Mg_1/3Nb_2/3)O₃-(0.8-x)Pb(Fe_1/2Nb_1/2)O₃-xPb(Fe_2/3W_1/3)O₃(PMN-(0.8-x)PFN-xPFW, where x=0.20～0.48) ceramic materials was studied in order to obtain high dielectric constant and low sintering temperature for enhancing the application in electrostrictive materials. Mn²⁺ was added into the basic PMN-PFN-PFW composition to discreasing the dielectric loss. The X-ray diffraction (XRD) and the scanning electronic microscope (SEM) were applied to analyze phases and microstructure, respectively. Moreover the aging, stability temperature, max hystersis and E-S were discussed in the paper.The result showed that the uniformer powder, lager grainzes and higher dielectric constant may be obtained using the two-step method than the one-step method (traditional technique with solid reaction process). Pure PMN-PFN-PFW perovskitic structure was obtained at calcination of 800℃temperatures. The max dielectric constant was obtained when PFW contents x=0.40 for 0.2PMN-(0.8-x) PFN-xPFW sintered at 900℃for 2h-3h. The Curie temperature Tm moved to low temperature with PFW contents increasing.Mn²⁺ doping had important effects on the properties of 0.2PMN-0.4PFN-0.4 PFW ceramics. The Curie temperature moves to low temperature and the dielectric loss decreases with Mn²⁺ contents increasing. Study of the experimental data indicated that The optimized results of density D(8.22/g.cm-3), Curie temperature Tm(40.0),dielectric constantεr(9212), dielectric loss tanδ(0.01), bulk resistivityρv(4.6×1012?·cm) were obtained with wt1.0% Mn²⁺ doping.Micro positioner of Leaded Multilayer Ceramic microstructure was prepared by the method of mechanical series electric parallel connection for 0.2PMN-0.4PFN-0.4 PFW ceramics doped Mn²⁺ ions. The strain value of s=3.6×10-4 was obtained with E=1500v/mm. With measured temperature increasing, the displacement decreased, but it discreased when time prolonged for the PMN-PFN-PFW electrostrictive materials.The temperature coefficient Tk =-4.5×10-3/℃can satified the desire of displacement temperature coefficient.