Study On Properties And Microstructure Of Bi_1/2(Na_1-xLi_x)_1/2TiO₃ Based Piezoelectric Ceramics

Lead-free piezoelectric ceramics Bi1/2(Na1-xLix)1/2TiO3 (BNLT)were prepared by the conventional ceramic sintering technique. The Li+ substituted Na+ at the A sites of the perovskite structure. The ferroelectric properties, dielectric properties, piezoelectric properties and microstructures of these piezoelectric ceramics were studied. BNLT ceramics doped with CeO2, La2O3 and Co2O3 were also studied, the piezoelectric properties and dielectric properties of these piezoelectric ceramics has been improved.The result on observation of P-E hysteresis loops indicates that while some Li+ ions substituted Na+ ions ,the remanent polarization Pr of BNLT ceramics is increased, and the coercive field Ec is decreased, which enhances piezoelectric properties. From the result of XRD, it was found that Bi1/2(Na1-xLix)1/2TiO3 ceramics show a single phase of perovskite structure with a rhombohedral symmetry in the range of x=0~0.20. Other phases which decrease piezoelectric properties of ceramics was found at x=0.30. From the result of SEM, the sintering temperature decreases with the increasing amounts of Li, and Li promotes the growth in some directions of crystalline grains. The measurements results of piezoelectric properties reveal that d33 reach a maximum 109 pC/N at x=0.15. The temperature dependence of dielectric constant were measured, it is found that the ceramics are relaxor ferroelectric. The effects of poling technique on the piezoelectric properties in the system were also investigated.Lead-free piezoelectric ceramics Bi1/2(Na1-xLix)1/2TiO3 (BNLT)doping with CeO2 were prepared by the conventional ceramic sintering technique. It is concluded that with the addition of proper amount of CeO2, the piezoelectric constant d33, the mechanical quality factor Qm and the dielectric constantεr are increased, and the dielectric loss tanδis decreased.Lead-free piezoelectric ceramics Bi1/2(Na1-xLix)1/2TiO3 (BNLT)doping with La2O3 were prepared by the conventional ceramic sintering technique. It is concluded that with the addition of proper amount of La2O3, the piezoelectric constant d33, the mechanical quality factor Qm are increased. But the piezoelectric properties and dielectric properties are decreased quickly when the amount of La2O3 is larger than 0.2wt%.