Preparation And Electrical Properties Of Barium Titanate Based Ceramics

Piezoelectric materials due to its dielectric, ferroelectric, piezoelectric and many othercoupling properties are very widely used in modern science and technology, which is one ofthe international research hots pot of intelligent materials. However, the electrical propertiesof BT and BNT ceramics are relatively low, not suitable for practical application. Therefor, itis expected to further improve the electrical properties of BT and BNT ceramics by dopingand defect compensation.Barium titanate ceramic is the material which has a very unique crystal structure. Inrecent years, based lead-free piezoelectric ceramics due to their superior dielectric,piezoelectric and ferroelectric properties, widely researched and application by the domesticand the foreign scholars, which is as a promising material of the lead-free piezoelectricceramics.Perovskite BaTiO3(BT) and Bi0.5Na0.5TiO3(BNT) lead-free piezoelectric ceramics arefamous for its unique crystal structure as the electronic information material.The lead-free piezoelectric ceramics were prepared by using the solid state reactionmethod, and the following ceramics were prepared: i)(1-x)BaTiO3-x(0.4BaZrO3-0.6CaTiO3)(BCZT) and (1-0.25x)BaTiO3-0.15xCaTiO3-0.1xBaSnO3(BCST), ii)(1-x)BaTiO3-xBiAlO3(BT-BiA) and0.9BaTiO3-(0.1-x)BiAlO3-xCaTiO3(BT-BiA-CT), iii)[(Bi0.5Na0.5)1-xYbx]TiO3(BNT-Y1),[(Bi0.5Na0.5)1-xYbx]Ti1-x/4(Ti)x/4O3(BNT-Y2) and (Bi0.5Na0.5)(Ti1-xYbx)O3-(BNT-Y3), respectively. In this paper, we studied on the effects of BT ceramics between thestructures and electrical properties with different doping amount of ZrO2, La2O3, SnO2, Al2O3,Bi2O3and CaCO3, as well as the relationship between the structure and properties of Yb2O3doped of BNT based ceramics.The ceramics were investigated by using the XRD, the impedance and the ferroelectrichysteresis loops. Results showed:(1) For the sample of BCZT ceramics with x=0.375, the piezoelectric coefficient d33=420pC/N, electromechanical coupling coefficient kp=57%, mechanical quality factor Qm=120.(2) The conductivity activation energies (Econ) of BLZT ceramics were1.71eV,1.31eV,1.13eV and1.19eV, respectively. For x=0.02, Econ=1.71eV, was a half of the energy gapEg=3.42eV. BLZT ceramics appeared abnormal dielectric peaks in the heating and coolingcycle.(3) High temperature part of the dielectric constants obeyed the Vogel-Fulcher law for the samples of BT-BiA ceramics with x=0.05and0.1. With increasing x, the relaxordispersion was gradually increasing and transformed to the diffusion ferroelectric ceramics.The electrostrictive coefficient Q values were clearly larger than that of lead-basedelectrostrictors at room temperature. Tthe thermal expansion dl/l and the thermal expansioncoefficient () increased with the increasing temperature. With increasing x, the Curietemperature of BT-BiA-CT ceramics increased gradually.(4) Yb2O3doped of BNT ceramics obtained polarization versus the electric field (P-E)hysteresis loops and symmetric “Butterfly” shaped electrostrictive curve. The remanentpolarization Prreached35μC/cm2, while the coercive field Ecreduced to20kV/cm for theBNT-Y2ceramic with x=0.01; BNT-Y1and BNT-Y2ceramics strain s reached0.23%. Withincreasing temperature, BNT-Y1, BNT-Y2and BNT-Y3ceramics obviously showed theantiferroelectric phase phenomenon. For Yb3+doped BNT ceramics, proved that for theBNT-Y2ceramic the Yb3+in the A-site, with Ti4+vacancies; for the BNT-Y3ceramics, Yb3+in the B-site, with oxygen vacancies.