Piezoelectric Properties And Thermal Stabilities Of High Temperature Bismuth Layer-structured Ferroelectric SrBi₄Ti₄O₁₅ Ceramics

Bismuth layer-structured ferroelectric materials (BLSF) can have wide applications in high temperature piezoelectrics and ferroelectric memory owing to their good fatigue resistance and high Curie temperatures. The ferroelectricity of BLSF materials mainly comes the deviation of B cations in the perovskite layer, the tilting of octahedron along the c-axis and the rotation of octahedron in the a-b plane between (Bi2O2)2+layers. The spontaneous polarization of BLSF materials can only rotate inside the a-b plane due to the limit of the layered structure and thus the material is hard to polarize and its piezoelectric property is poor. Research on BLSF mainly focused on how to improve their piezoelectric activity by increasing their density, resistivity as well as their remnant polarization and reducing their coercive field while keeping their Cuire temperature unchanged. Layered-structured SrBi4Ti4O15ceramics with Curie temperature Tc521℃,d33=15pC/N was chosen in this study, traditional solid-phase sintering process its doping research in order to get excellent piezoelectric properties while maintaining a high Curie temperature.In this thesis, using suitable dodecahedron with a bit of Ce ions replaces SrBi4Ti4O15A bit Sr ions substituted replace modification. The results showed that Ce Sr substitution reduces the sintering temperature, while increasing the density of the ceramic material, and significantly reduces the coercive field of the SBT material, such material is more likely to be polarized. For Sr1-xCexBi4Ti4O15ceramics, when x=0.04, the modification effect SBT most significant Ceramic piezoelectric constant d33reaches27pC/N, dielectric loss is significantly reduced. SBT bismuth layered structure of piezoelectric ceramic planar electromechanical coupling coefficient of the modified kp, radial stretching vibration mode frequency constant Np and thickness extension vibration mode frequency constant Nt with increasing temperature changes relatively stable, from room temperature to a temperature within the range of475℃kp5%variation in the vicinity of the temperature change rate of Np and Nt are-68ppm/K and-25ppm/K. As the temperature increases (from room temperature to475℃),the fundamental frequency of the series resonant fs0, parallel fp0resonance fundamental frequency decreases linearly, its rate of temperature change are-68ppm/K. Modified material heat aging performance, and maintain a high piezoelectric properties at high temperatures.In the study of A-site ions doping also studied the B-site ions doping effect on the performance SrBi4Ti4O15.In this paper, were selected Co ions and Mn ions substituted replace B bit Ti ion. From the X-ray diffraction pattern analysis, no significant sample of the substitution impurity was found(m=4). The dielectric loss of piezoelectric ceramics substituted with Co element is lower than the dielectric loss of the pure piezoelectric ceramic SBT. As the doping amount of the increase, SBT-yCo sintering temperature of the piezoelectric ceramic is reduced, increased density after sintering, and a slight increase in the Curie temperature Tc. After substituted Co-substitution piezoelectric active material increases, when y=0.03, the modification effect SBT-yCo most significant series ceramics, piezoelectric constant d33reaches 28pC/N, the doping element can be improved Co pressure SBT the piezoelectric constant power.Prepared by solid state reaction with Mn as a doping element, replace the B-site Ti ions of SrBi4Ti4O15piezoelectric ceramic elements substituted samples no obvious impurity phase, and a typical four-layer structure bismuth layer piezoelectric ceramics. At room temperature, the dielectric loss of piezoelectric ceramics substituted with Mn lower than the value of pure piezoelectric ceramic SBT. As the doping amount of the increase, SBT-zMn sintering temperature increases the density decreases, and a slight increase in the Curie temperature Tc. After doping Mn replaced piezoelectrically active material increases, when z=0.04, the modification effect SBT-zMn most significant series ceramics, piezoelectric constant d33reaches30pC/N. High temperature electrical properties of Mn-substituted modified tests showed SBT piezoelectric ceramic dielectric, piezoelectric properties with excellent temperature stability.