Samples of xBiFeO 3 -(1 -x)BaTiO 3 (x = 0, 0.02, 0.04, 0.06, 0.07 and 0.08) were synthesized by solid state reaction technique and sintered in air in the temperature range 1,220-1,280°C for 4 h. X-ray diffraction data showed that 2-8 mol% BiFeO 3 can dissolve into the lattice of BaTiO 3 and form single perovskite phase. The crystal structure changes from tetragonal to cubic phase at room temperature when 8 mol% of BiFeO 3 was added into BaTiO 3 . Scanning electron microscope images indicated that the ceramics have compact and uniform microstructures, and the grain size of the ceramics decreases with the increase of BiFeO 3 content. Dielectric constants were measured as functions of temperatures (25-200°C). With rising addition of BiFeO 3 , the Curie temperature decreases. For the sample with x = 0.08, the phase transition occurred below room temperature. The boundary between tetragonal and cubic phase of the BiFeO 3 -BaTiO 3 system at room temperature locates at a composition between 7 and 8 mol% of BiFeO 3 . The diffusivity parameter c for compositions x = 0.02 and x = 0.07 is 1.21 and 1.29, respectively. The relaxor-like behaviour is enhanced by the BiFeO 3 addition.
Pure and Zr-substituted CaCu 3 (Ti 1-x Zr x ) 4 O 12 (x = 0, 0.01, 0.02, 0.03) ceramics were prepared by the Pechini method. X-ray powder diffraction analysis indicated the formation of single-phase compound, and all the diffraction peaks were completely indexed by the bodycentered cubic perovskite-related structure. The effects of Zr 4? ion substituting partially Ti 4? ion on the dielectric properties were investigated in frequency range between 100 Hz and 1 GHz. The low frequency (f B 10 5 Hz) dielectric constant decreases with Zr substitution and the high frequency (f C 10 7 Hz) dielectric constant is unchanged. Interestingly, a low-frequency relaxation was observed at room temperature through Zr substitution. The observed dielectric properties in Zr-substituted samples were discussed using the internal barrier layer capacitor model. A corresponding equivalent circuit was adopted to explain the dielectric dispersion. The characteristic frequency of low-frequency relaxation rises due to the decrease of the resistivity of grain boundary with Zr substitution, which is likely responsible for the large low-frequency response at room temperature.
Using starting BaTiO 3 powders of various particle sizes, we investigated the densification and dielectric characteristics of BaTiO 3 ceramics sintered at low temperature with the addition of ZnO-B 2 O 3 -SiO 2 (ZBS) glass as sintering aids. Scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and LCR meter were used to examine the structure and dielectric properties. The results indicated that the particle size of raw powders had a dramatic influence on the densification and dielectric properties of BaTiO 3 ceramics. The grain size of the final ceramics was almost proportional to the particle size of the starting BaTiO 3 powder. Moreover, the tetragonality (c/a ratio) and Curie temperature is increased with the increase of grain size of the BaTiO 3 ceramics. The relative density of 96% and the dielectric constant of 1440 were obtained for the BaTiO 3 ceramics prepared with the raw powders of average particle size of 800 nm. In addition, the sintering temperature was reduced to 1100 8C due to the addition of 5 wt% ZBS glass.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.