Preparation And Performance Adjustment Of0.36BiScO₃-0.64PbTiO₃Based High Temperature Ferroelectric And Piezoelectric Ceramics

In recent years, high-temperature piezoelectric materials have received a great deal ofattention due to their applications as sensors and actuators in the energy, aerospace andautomobile industry. The high Tc(~450oC) and excellent piezoelectric properties(d33=450pC/N) of the0.36BiScO3-0.64PbTiO3ceramic make it attractive for hightemperature applications. However, there are also several shortcomings of BS-PT, suchas low value of the hard piezoelectric properties, high cost of Sc2O3and so on. To solvethese problems, in this paper,0.36BiScO3-0.64PbTiO3piezoelectric ceramics werefabricated by the solid state reaction method where overdosing the raw chemicals,solely PbO with1.0wt%excess (BS-PT-I) and both Bi2O3and PbO with1.0wt%excess (BS-PT-II) were employed to address their influence on the sintering behavior,microstructure and electrical properties of the ceramics. Based on the understandingobtained, BiGaO3were selected as the third component to form novel ternary systemswith0.36BS-0.64PT. The microstructure and electric properties at room temperatureand high temperature of the ternary systems0.36Bi(Sc0.99Ga0.01)O3-0.64PbTiO3weresystematically studied in this thesis work.Dense BS-PT-I and BS-PT-II piezoelectric ceramics were fabricated by thetraditional solid state reaction method. Room temperature XRD patterns shows that bothtetragonal and rhombohedral phases exist in the two systems. The SEM images showsdense ceramics with irregular grain size distribution around1~6μm have been obtainedfor all the samples. Through performance testing, we found that the BS-PT-I sintered at1000oC for2h possess good properties: d33=469pC/N, kp=0.52, Qm=24.51. Especially,the dielectric tunability was increased from59.8%to78%from room temperature to200oC. The BS-PT-II sintered at1150oC for2h possess good properties: d33=378pC/N,kp=0.52, Qm=21.08. The dielectric tunability was increased from58.6%to75.9%fromroom temperature to160oC. The augment of dielectric tunability at high temperatureindicates that the BS-PT has potential to be used as tunable capacitors at elevatedtemperature. With the increase of temperature, the remanent polarization Prof bothBS-PT-I and BS-PT-II ceramics decreased at first and then increased gradually; thestrain were changed about0.3~0.4%, indicating their good thermal stability.Compared with the0.36BS-0.64PT, the piezoelectric and ferroelectric properties of0.36Bi(Sc0.99Ga0.01)O3-0.64PbTiO3prepared via soldid state reaction method worsenedslightly. However, the obvious improvement of figure of merit (FOM) and the rising dielectric tunability from58.6%to75.9%when increasing temterature from roomtemperature to160oC, indicate the BiGaO3-modified BS-PT is a candicate for dielectrictunabibilty applications in high-temperature.