Synthesis of Barium Titanate Compounds with Enhanced Dielectric Properties at Room Temperature
The addition of 22 mol% of different zirconia containing powders: cubic stabilized zirconia (8YSZ), tetragonal zirconia (TZ3Y), and pure zirconia to barium titanate (BaTiO3) was studied. X-ray diffraction analysis of the sintered compact made of these powder mixtures confirmed the presence of single phase peroviskate-like structure. The microstructure of the sintered samples showed different grain sizes, for different kinds of zirconia additives. The relative permittivity and the dielectric loss of the sintered pellets were measured at different temperatures and frequencies. The highest relative permittivity was obtained for samples having 22 mol% 8YSZ. The yttria addition to barium titanate zirconate had been discussed.
Dielectric Behavior of Yttrium doped Barium-zirconium-titanateCeramics
The ferroelectric behavior of the yttrium-doped barium-zirconium-titanate perovskite ceramics Ba1 xY2x/3Ti.75Zr0.25O3 (with x = 0.0, 0.01, 0. 025, 0.05) has been studied. The room temperature X-ray diraition study suggests that all the compositions have a single-phase cubic symmetry with space group Pm-3m The temperature dependent dielectric constant of the ceramics was investigated in the frequency range from 50 Hz to 1 MHz. The density of the samples was determined using Archimedes’ principle and was found to be 98% of the X-ray density. A broad dielectric anomaly coupled with a shift of the dielectric maximum towards a higher temperature with increasing frequency indicates relaxor-type behavior in the ceramics With increasing in yttrium content, the Curie temperature decreased, except for x = 0.01 where the Curie temperature increased. The relative permittivity decreased and broadened with increasing yttrium content.
Grain-size effects on dielectric and piezoelectric properties of poled BaTiO3 ceramics
Abstract Barium titanate (BaTiO3) is known historically as the first ceramic piezoelectric material and shows a high possibility of being revitalized as a popular lead-free piezoelectric material. However, few systematic studies of the grain-size effects on the dielectric and piezoelectric properties of poled BaTiO3 ceramics have been carried out to date. In this work, a series of dense BaTiO3 ceramics with uniform grain-size distribution were successfully prepared by the conventional solid-state reaction, and the grain-size effects on the dielectric and piezoelectric properties were explored in their poled states. An interesting physical phenomenon has been found: dielectric permittivity e′ and the piezoelectric constant d33 increase significantly at room temperature with the reduction of the average grain size g and reach the maxima at g = 0.94 μm. It was revealed that domain structure and relative density play substantial roles in determining the e′ and d33 behaviors. The average 90° domain width decreases monotonically with g. Both the 90° domain wall density and the area dimension of area dimension domain wall are considered as important factors that greatly influence the d33 value. Extrinsic contribution comprises the major part of the observed d33 values in the fine-grained BaTiO3 ceramics.