Dy掺杂Sr_2Bi_4Ti_5O_(18)陶瓷的介电性能

The dielectric property of Dy-doped Sr_2Bi_4Ti_5O_(18)ceramics

采用固相烧结工艺制备了Sr2Bi4-xDyxTi5O18(x=0,0.25)陶瓷样品,用X射线衍射对其微结构进行了分析,并测量了样品的铁电、介电性能.Sr2Bi3.75Dy0.25Ti5O18样品的X射线谱上出现SrTiO3衍射峰,其介电损耗随温度的关系曲线上存在明显的弛豫损耗峰P ,该损耗峰的激活能为0.4eV,可以确定该峰是由氧空位引起的.结果表明:离子半径较小的Dy3+很难进入类钙钛矿层,造成样品中大量的A位空位,使得氧空位浓度增加.氧空位的存在会导致很强的畴钉扎,从而极化降低.

Sr_2Bi_(4-x)Dy_xTi_5O_(18) (x=0,0.25) ferroelectric ceramic samples are prepared by traditional solid-state reaction method. The microstructure is analyzed by X-ray diffraction, and ferroelectric and dielectric properties are measured. From XRD patterns of Sr_2Bi_(3.75)Dy_(0.25)Ti_5O_(18), the SrTiO_3 phase is observed. There exists a dielectric loss peak P_Ⅰ on the Sr_2Bi_(3.75)Dy_(0.25)Ti_5O_(18)dielectric data, which is relaxational characteristic, and the activation energy calculated by means of the peak shift method is equal to 0.4 eV, so the relaxation mechanism is attributed to the migration of oxygen vacancy. Those results indicate Dy^(3+)substitution for Bi^(3+)is difficult due to the mismatch of ion radii. It causes many A-site defects, and leads to a increase of the concentration of oxygen vacancies, which causes strong domain pinning, and brings about a decrease in polarization.