Study On The Piezoelectric Properties Of PLZT-based Relaxor Ferroelectric Ceramics

Piezoelectric material, which can transform mechanical energy to/from electric energy is widely applied in electron component, such as ultrasonic transducers, drivers etc.. With the development of technology and the improvement of the living standard, electrical machines become smaller, which requires the piezoelectric ceramic for more excellent properties.In this paper, the dielectric, piezoelectric and ferroelectric properties of Pb1-xLax(Zr1-yTiy)1-x/4O3+1wt% Sb2O5 (PLSZT) with different La substitutions and radio of Zr/Ti are tested. By XRD, SEM, and testing the dependence of electric properties on temperature, the relationship between the microstructure and the piezoelectric, ferroelectric properties are analyzed. The morphotropic phase boundary(MPB) moves to higher radio of Zr/Ti when increasing the La substitution and the XRD results show that polarization will also induce the transformation from rhombohedral to tetragonal. Therefore, with different radio of Zr/Ti, the optimal properties can be obtained with corresponding La substitution. When x=0.065,y=0.41, excellent properties are obtained. (d33=842 pC/N,kp=0.71,kp=0.54, Qm=38, εr=5089, tgδ=0.029) The testing and fitting of the εr-T curve indicate that PLSZT with La substitution in this paper are typical ferroelectric with diffuse phase transition.By studying the properties of Pb0.935-xLa0.065Ax(Zr0.58Ti0.40)O3+lwt% Sb2O5(A is Sr2+ or Ba2+), the similar effects are found in the PLSZT with each of the ion. When the x=0.005, the d33 increases but with more substitution it will decline. Both of them contribute to the increasing of εrand declining of tgδ. When the x=0.005, optimal properties were attained, as follow:Sr:d33= 857 pC/N, kp=0.61,kt= 0.52,0m= 45,εr= 5868, tgδ= 0.021.Ba:d33= 871pC/N,kp= 0.69,kt=0.53, Qm=47,εr= 5334, tgδ=0.018。At last, by testing the dependence of the dielectric, piezoelectric and ferroelectric properties of Pb0.935-xLa0.065Bax(Zr0.58Ti0.40)O3+1wt% Sb2O5 on temperature, in the polarized specimens, a little peak is found on both of the εr-T and tgδ-T curve at Tnr= 119℃ (Tnr<Tm, Tm is temperature with maximum εr, Tm=178℃). The frequency diffuse degree of εr-is different when T<Tnr or T>Tnr, which means the transformation between macrodomain and microdomain. When temperature was closed to Tnr, Pr、Ec、kp would greatly decline.