Ytterbium doping effects on structural, optical and electrical properties of Bi4Ti3O12 system

Abstract

Bi4-xYbxTi3O12 with x = 0.0, x = 0.1, x = 0.2 and x = 0.3 specimens were synthesized by conventional solid-state reaction. The influence of ytterbium doping on the structural, optical, dielectric and electrical properties of the synthesized compounds were investigated. The X-ray diffraction analysis showed that all samples are homogenous and crystallize in the orthorhombic system with the Fmmm space group. Also, it is found that the unit cell volume (V) goes on decreasing owing to the decrease of lattice parameters (a, b and c) with increasing Yb content. The absorbance measurement reveals that the intensity increases with increasing ytterbium concentrations. Also, it exhibits an additional peak occurred at the wavelength 975 nm. This peak has been attributed to the characteristic transitions from ground state 2F7/2 to excited states 2F5/2 of Yb3+ ions. From DC-resistivity measurements, it is noticed that all compositions exhibit a semiconductor behavior. In addition, it is found that below 420 K, the electrical resistivity was enhanced considerably upon substitution up to x = 0.3. Such behavior was attributed to the decrease of oxygen vacancies density. At 420 K, the parent compound exhibits a saturation region, which shifts to higher temperatures upon rising Yb content. The deduced activation energy values at high temperatures altercated around 990–828 meV. These values are attributed to oxygen vacancies migration. The electrical conductivity behavior of the samples was explained on the basis of jump relaxation model. As well the conductivity spectrum obeys to the Jonscher universal double power law.