Influence Of Cao On Structure And Electrical Conductivity Of Pyrochlore-type Sm_2zr_2o_7

摘要

(Sm_(1-x)Ca_x)_2Zr_2O_(7-x) (0 ≦x≦0.100) ceramics were prepared by a solid state reaction process at 1973K for 10h in air, and were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). (Sm_(1-x)Ca)_2Zr_2O_(7_x) (0≦x≦0.025) ceramics have a single phase of pyrochlore-type structure; however (Sm_(1-x)Ca_x)_2Zr_2O_(7-x) (0.050 ≦x≦ 0.100) consist of pyrochlore phase and a small amount of perovskite-like CaZrO_3. The electrical conductivity of (Sm_(1-x)Ca_x)_2Zr_2O_（7_x) ceramics was investigated by complex impedance spectroscopy over a frequency range of 0.1 Hz to 20 MHz in the temperature range of 573-873 K. The measured electrical conductivity obeys the Arrhenius relation. Both the activation energy and pre-exponential factor for grain conductivity increase with increasing the CaO content; however, electrical conductivity of (Sm_(1-x)Ca_x)_2Zr_2O_(7-x) decreases with increasing the CaO content, which is due to the increase in structural disordering at 0≦x≦ 0.025 and the presence of the poorly conducting CaZrO_3 phase at 0.050 ≦ x ≦ 0.100, respectively.