Bismuth-based pyrochlore dielectrics with the formula (Bi1.5Zn0.5)(Ti1.5M0.5)O7 (M = Nb, Ta and Sb) have been synthesized to investigate the influence of M between the dielectric properties and crystal structure. The XRD patterns show that all of the three samples give single phase. The refined data by GSAS program and the bond valence theory were used to analyze the differences in dielectric properties with occupation of different ions in B site. The dielectric constant of BZTS is the smallest in the BZTM, which is due to the polarizability and the contribution of BO6octahedra which has weak correlation when Sb placed into the center of the octahedra would also result in small αε. When it comes to the moderate temperature range, oxygen vacancies migration was thermally activated as the carriers mechanism, and the different activation energies is related to the association and the disassociation of massive complex defects. The Rietveld refinement data pointed that with the respectively change of B ions, more oxygen vacancies and free oxygen ions are provided by structural defects to participate in the conduction which can lead to the σ increase gradually.
Deposition of binder-free oxygen-vacancies NiCo2O4 based films with hollow microspheres via solution precursor thermal spray for supercapacitors
