Study Of The Composition-property Relationship Near The Morphotropic Phase Boundary In PZT Based Perovskite Solid Solution Ceramic

Most studies have showed that the Pb(Zr,Ti)3(PZT) based perovskite type solidsolution ceramic usually has a excellent electrical performance near the morphotropicphase boundary (MPB). So in this paper, we will select two kinds of the PZT basedpiezoelectric ceramics to explore the relationship between composition and propertynear the MPB.In the first part of this paper, we selected the PSbN-PZN-PZT quaternary ceramicas an experimental object. The effects of Zr/Ti ratio, process of sintering andpolarization on electrical properties were studied. Then, we doped La3+on thePSbN-PZN-PZT quaternary ceramic to enhance the properties. The results indicated thatthe Zr/Ti ratio have a great influenced on phase structure, microstructure and electricalperformance of the0.02PSbN-0.2PZN-0.78PZxT1-xpiezoelectric ceramics. Withincreasing the Zr/Ti ratio, a phase transition from tetragonal to rhombohedral wasdetected and a MPB was identified approximately in the composition ofZr/Ti=0.50/0.50, which was also confirmed by corresponding dielectric, piezoelectric,and ferroelectric properties. And the Zr/Ti=0.50/0.50composition possessed anoptimum properties of ρv=7.97g/cm3, εT33/ε0=2433, tanδ=1.77%, d33=520pC/N, kp=0.64,Tc=284oC, Pr=32.3μC/cm2, Ps=40.3μC/cm2and Ec=1.47kV/mm. The studies of sinteringtemperature and poling conduction on this composition show that the grain density anda better electrical performance were founded when sintered at1260oC, and the optimalproperties were obtained when poled at3kV/mm for20min in a silicone oil bath at120oC.In addition, the doping modification of La3+on(Pb0.93-3x/2Sr0.05Ba0.02Lax)[(Sb0.5Nb0.5)0.02(Zn13Nb23)0.20(Zr0.535Ti0.465)0.78]O3piezoelectricceramic was studied. The results showed that when the La3+increased, the phasestructure was not changed, but the piezoelectric and dielectric properties were largelyenhanced, meanwhile, the Tc was obviously reduced. Combined with the Tcand theelectrical properties, we can found that the sample with x=1mol%opposed a bestcomprehensive performance: Tc=163oC, εT33/ε0=4033, tanδ=2.72%, d33=630pC/N,kp=0.565and Qm=43. Moreover, it found that annealing treatment is almost no influenceon microstructure and the di/piezoelectric properties. Based on the high Tcand good performance of the PZT andBi(Mg1/2Ti1/2)O3-PbTiO3(BMT-PT) which located at the MPB, So in the second part ofthis paper, we selected xBMT-(0.56-x)PZ-0.44PT as an experimental object. The phasetransition behavior, relaxation behavior, dielectric, ferroelectric and piezoelectricproperties were investigated as a function of the BMT content. The results show thatwith increasing the BMT content, a phase transition from tetragonal to rhombohedralwas detected and a MPB was identified at x=0.08. In addition, the dielectric diffusenessand frequency dispersion behavior were induced and a normal-relaxor-diffuseferroelectric transformation was observed. However, the change of the Tmis complex.Moreover, the x=0.08composition not only possessed the optimum properties withεT33/ε0=1450, Qm=69, d33=390pC/N, kp=0.46, Pr=30μC/cm2, Ec=1.4kV/mm, Tc=325oC and d33*=436pm/V, but also owned a good thermal stability and frequency stability.