Ferroelectric and anisotropic electrical behaviors of barium magnesium fluoride (BaMgF4) single crystal grown under CF4 atmosphere by the Czochralski method are comprehensively studied by polarization hysteresis and impedance spectroscopy measurements, respectively. The coercive field (Ec) varies not only with applied frequency but also with ramp rates, while spontaneous polarization Ps∼6.9 C/cm2 remains the same. Dielectric polarization and ionic conductivity measurements at various temperatures and frequencies reveal quasi-one-dimensional ionic conduction phenomena along the c-axis and non-Debye dielectric relaxation along the axes.

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.

Bismuth titanate (Bi4Ti3O12) crystals were grown by our original floating-zone pulling down (Fz-PD) method. The shape of the grown crystals was fiberlike with dimensions of 15×1×0.34 mm3. The dielectric properties and impedance of the grown fiber crystals were determined. A large difference in the dielectric constant was observed along the c- and a-axes.

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