Impedance and dielectric relaxation spectroscopy studies on the calcium modified Na0.5Bi0.44Ca0.06TiO2.97 ceramics

摘要

Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub ceramics were synthetized by conventional solid-state reaction. XRD measurement analysis shows that the Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub sample is the single perovskite structures. The oxide ion conductivity of the Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub sample was investigated by AC impedance spectroscopy measurement. The bulk conductivity of Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub sample can arrive at 2.22×10sup-4/sup S/cm at 573 K in air atmosphere. By changing measuring temperature of dielectric frequency spectroscopy measurement, the activation energy E and pre-exponential factor τsub0/sub are E = 0.81 eV, τsub0/sub=1.5×10sup-13/sup s for Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub sample, respectively. Judging from the relaxation parameters, the dielectric loss peaks correspond to oxide ion via vacancies diffusion in Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub sample. Compared with the same dopant amount Nasub0.5/subBisub0.5/subTisub0.94/subMgsub0.06/subOsub2.94/sub compound, the better oxygen vacancy mobility and larger specific free volume Vsubsf/sub might be responsible for the favourable oxide ion conductivity in the Nasub0.5/subBisub0.44/subCasub0.06/subTiOsub2.97/sub sample, indicating that calcium modified Nasub0.5/subBisub0.5/subTiOsub3/sub materials are promising for intermediate-temperature solid electrochemical devices.