Polycrystalline BiFe1−xCrxO3 ceramics with x = 0–1 have been produced via a mixed oxide route. The effects of Cr substitution on the structure and on the electrical and ferroelectric properties of BiFe1−xCrxO3 samples have been studied by performing x-ray diffraction, dc resistivity and dielectric measurements as well as characterizing the polarization-field hysteresis loop. The results indicate that the structure of BiFeO3 can be altered dramatically with a small amount of Cr doping (x = 0.005–0.1). Substitution of Cr for Fe results in large variations in the resistivity of BiFeO3 ceramics. The resistivity of BiFe1−xCrxO3 samples reaches a maximum value of 2 × 1012 Ω cm at x = 0.1, which is about two and a half times higher than that for pure BiFeO3. Doping with 1 mol% Cr increases the dielectric constant and the remnant polarization to four and ten times, respectively, as large as those of a pure sample. There is a strong correlation between the electrical resisitivity, the dielectric constants and the remnant polarization of BiFe1−xCrxO3 ceramics.
The velocities of longitudinal and shear ultrasonic waves propagated in very dense (95% of theoretical), highly-textured, ceramic Bi,Sr,CaCu,O,+, (812212) have been measured as functions of temperature (between 10 and 290 K) and hydrostatic pressure at 290 K. The main finding is a marked anisotropy of the elastic stiffness constants and their dependences on pressure. We have observed an elastic stiffness constant in the a 4 plane that is substantially greater than that in the c direction. This observation is consistent with the crystallographic structure of 812212. The anomalous elastic effects and thermal hysteresis, observed previously 1 by several groups in various Bi-based superconductors in the range of 19' 2-240 K, have not been found in t h e present material. Our observations suggest that these anomalies are not an inherent properly of Bi-based cuprates. but instead may depend on the oxygen content and microstructure of the ceramic material. An analysis of sound velocity in a polycrystalline array of elastically anisotropic crystallites is presented.
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.