Abstract:
In order to explore the effect of point defects on microstructure and electrical properties of the ceramics, the nitrogen and oxygen atmospheres were used separately during the calcination and sintering processes via a solid-state reaction method. Effects of the calcination and sintering atmospheres on microstructure, dielectric, piezoelectric, and ferroelectric properties of the ceramics were studied. The results of X-ray diffraction and UV-vis diffuse reflectance spectra imply that the concentration of point defects is different in the ceramics prepared in the different atmospheres. All the ceramics exhibit pure perovskite structure, while their microstructures are significantly different. The ceramics show similar dielectric constant-temperature curves with different depolarization temperatures. The ceramics prepared in the nitrogen atmosphere and those prepared in the oxygen atmosphere exhibit the mean grain size of 2.1 μm and 1.0 μm, the Curie temperature of 248 ℃ and 258 ℃, the depolarization temperature of 76 ℃ and 87 ℃, the remnant polarization of 27.2 μC/cm2 and 27.6 μC/cm2, the piezoelectric constant of 122 pC/N and 128 pC/N, respectively. The results demonstrate that it is crucial to change the microstructure and electrical properties of the (Na0.5Bi0.5)0.94Ba0.06TiO3 ceramics by changing the atmospheres at the calcination and sintering processes.
