Preparation And Properties Of Bismuth Layered Na_0.5Bi_2.5Nb₂O₉-Bi₃TiNbO₉ High Temperature Piezoelectric Ceramics

In this paper,Na_0.5Bi_2.5Nb₂O₉-Bi₃TiNbO₉ bismuth layered high temperature piezoelectric ceramics were prepared by traditional solid-state reaction method.The effects of the content of two-phase ceramics and the doping of composite ions on the phase structure,microstructure,piezoelectricity,dielectricity and ferroelectricity of the ceramics were studied.Firstly,the optimal synthesis method and synthesis temperature for the preparation of ceramics Na_0.5Bi_2.5Nb₂O₉-Bi₃TiNbO₉ were determined.Then,the effects of different proportion of two-phase ceramic content on the structure and properties of x Na_0.5Bi_2.5Nb₂O₉-（1-x）Bi₃TiNbO₉ceramics were investigated.XRD and SEM results show that x Na_0.5Bi_2.5Nb₂O₉-（1-x）Bi₃TiNbO₉ is a bismuth layered symbiotic ceramic with typical lamellar structure.When x=0.3,0.3Na_0.5Bi_2.5Nb₂O₉-0.7Bi₃TiNbO₉ceramics have ultra-high Curie temperature and improved piezoelectric properties.And the properties of the ceramics are:d₃₃=11.8p C/N,ε_r=124,tanδ=0.34%,k_p=6.1%,Q_m=2234,T_c=876°C,E_c=28.7 k V/cm,P_r=0.76μC/cm².When x=0.7,0.7Na_0.5Bi_2.5Nb₂O₉-0.3Bi₃TiNbO₉ceramics have good piezoelectric properties,but Curie temperature decreases seriously.The piezoelectric properties of the ceramics are as follows:d₃₃=19.3 p C/N,ε_r=124,tanδ=0.36%,k_p=6.5%,Q_m=1600,T_c=802°C,E_c=33.5 k V/cm,P_r=1.91μC/cm²。In addition,the ceramics of 0.3Na_0.5Bi_2.5Nb₂O₉-0.7Bi₃TiNbO₉ and0.7Na_0.5Bi_2.5Nb₂O₉-0.3Bi₃TiNbO₉ were doped with（Li Ce）and（Li Y）respectively.XRD and SEM results show that there is no obvious heterophase after doping,and（Li Ce）doping can improve the piezoelectric properties of the ceramics,and（Li Y）doping can increase the Curie temperature of the ceramics.When x=0.04,the optimum properties of Na_0.15-xLi_xBi_2.85-xCe_xTi_0.7Nb_1.3O₉ ceramics are as follows:d₃₃=20.7 p C/N,ε_r=140,tanδ=0.34%,T_c=861°C,E_c=62 k V/cm,P_r=3.4μC/cm².When x=0.02,the optimum properties of Na_0.35-xLi_xBi_2.65-xY_xTi_0.7Nb_1.3O₉ceramics are as follows:d₃₃=20.8 p C/N,ε_r=149,tanδ=0.49%,T_c=808°C,E_c=54 k V/cm,P_r=8.1μC/cm².After annealing at 800°C for 2 h,the piezoelectric constant d₃₃ of the ceramic still remains above 17 p C/N,which indicates that the ceramic has a good application prospect at high temperature.