Flux growth of pure and lanthanum (La3+)-substituted Bi4Ti3O12 single crystals and their characterization

In this paper, we report the growth of pure Bi4Ti3O12(BIT) and Bi4-xLaxTi3O12 (x=0.25, 0.50 and 0.75) single crystals by high-temperature solution growth (flux growth). The effects of La substitution on structural, optical transmission, ionic conductivity, dielectric constant and ferroelectric properties have been studied. Powder X-ray diffraction (XRD) and Differential thermal analysis (DTA) results reveal that the presence of La increases lattice constant (along the b- and c-axes) and liquidus and crystallization temperature of BIT. The deviation in La concentration in grown crystals from the initial La concentration was revealed by Energy dispersive X-ray analysis (EDAX). The incorporation of La ions also shifts the fundamental absorption edge in the UV-vis spectrum towards the higher-energy region and changes the absorption coefficient of BIT. Decreases in the dielectric constant, loss factor and ionic conductivity of BIT were observed with an increase in La concentration. Although, a significant improvement in remnant polarization was observed in P-E studies, La incorporation markedly increased the coercive field of BIT. (author)