Study On The High-power And High Stability Of Piezoelectric Ceramics

To meet the request of the high electromechanical coupling factor (KP), high mechanical quality factor (Qm), low dielectric loss under high electric field condition and excellent ageing rate and temperature coefficient of resonant frequency ceramics for high power application, Pb(Sn_1/3Nb_2/3)O₃-Pb(Zn_1/3Nb_2/3)O₃ -PbTiO₃-PbZrO₃ quaternary piezoelectric ceramics were prepared by conventional solid state reaction method with varying the ratio of Zr/Ti, dopant content and optimizing processing. At 960 ℃ calcing temperature, 1260 ℃ sintering temperature, the microstructure , dielectric and piezoelectric properties of PSN-PZN-PZT ceramics achieve maximum values by the twice synthesis method. The optimum poling condition: poling temperature is 130℃,poling time is 30min,poling electric field is 3kV/mmm。 With the addition of Sr2+,Ba2+, the Cure temperature the PSN-PZN-PZT ceramics were deceased greatly, although the piezoelectric properties of them were enhanced. d₃₃ and ε^T₃₃/ε₀ of samples were increased by increasing Cr content. Beyond 0.5wt%, the values of d33 and ε 3T3/ε 0 decreased. By XRD,SEM and EPR, the result indicated high valence of Cr ion play an important role in ceramics, as the Cr content is low. When Cr content increasing, the properties are dominated by the low valence of Cr ion. When Cr content is above 0.7wt%, surplus Cr will accumulate at the grain boundary, the microstructure and the properties of samples can be deteriorated. In high electric field, the values of dielectric loss were increased as Cr content. Cr dopant can reduce the ageing rate of PSZN-PZT ceramics and the coefficients TCFr. Taking to consideration, the piezoelectric properties and temperature stability of resonant frequency, it can be concluded that 0.5wt% of Cr doped PSZN-PZT ceramics has excellent comprehensive properties for application. The property parameters are listed below: Piezoelectric constant d33=350pC/N, mechanical quality factor Qm=1990, coupling coefficient Kp=0.553, Cure temperature Tc=323℃. dielectric loss factor tgδ(%)=0.4 (1V/mm), 1.0(200V/mm), 1.5(400V/mm), 2.0(600V/mm), ageing rate A =0.188% and the temperature coefficients TCFr=13 ppm/℃.