Pradeep Kumar; Avinash Kishore; Aloka Sinha
Abstract
In the present study, the insulating titanium dioxide (TiO2) nanoparticles were dispersed in two different concentrations of 0.5 wt % and 1.0 wt % in pure ferroelectric liquid crystal (FLC) mixture, W206E. The effects of different concentrations of dopant TiO2 in W206E for ...
Read More
In the present study, the insulating titanium dioxide (TiO2) nanoparticles were dispersed in two different concentrations of 0.5 wt % and 1.0 wt % in pure ferroelectric liquid crystal (FLC) mixture, W206E. The effects of different concentrations of dopant TiO2 in W206E for electro-optical and dielectric properties have been studied. The optical microscopy measurements clearly show the isotropic transition temperature of both the doped samples slightly increases by about 1 ~ 2 0 C as compared to the pure sample. Further, with the increasing concentrations of dopant TiO2, the value of spontaneous polarization decreases. The value of dielectric permittivity also decreases for both the doped samples and this decrease in the value of permittivity is more prominent with increasing concentrations of TiO2 at the lower frequencies. The dielectric measurements also confirm the presence of Goldstone mode in Smectic C* phase in pure as well as in both the doped samples. The conductance measurements confirm the decrease in conductivity of doped samples as compared to the pure W206E FLC. This study may help in improving the transition temperature and reducing the impact of free ionic charge impurities on various physical properties of liquid crystal host by screening the free ions using TiO2 nanoparticles as dopant.
Jasneet Kaur; Jaspreet Kaur; R. K. Kotnala; Vinay Gupta; Kuldeep Chand Verma
Abstract
In the present work, the self-assembly of Co 2+ and Fe 3+ doped SnO2 nanoparticles (Co and Fe = 5 mol% each) into nanorods by co-doping of Ce 3+ (4 mol%) ions is studied. The nanorods are prepared by a chemical route using polyvinyl alcohol as surfactant with the composition Sn0.91Co0.05Ce0.04O2 (SCC54) ...
Read More
In the present work, the self-assembly of Co 2+ and Fe 3+ doped SnO2 nanoparticles (Co and Fe = 5 mol% each) into nanorods by co-doping of Ce 3+ (4 mol%) ions is studied. The nanorods are prepared by a chemical route using polyvinyl alcohol as surfactant with the composition Sn0.91Co0.05Ce0.04O2 (SCC54) and Sn0.91Fe0.05Ce0.04O2 (SFC54). The X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic and electrical measurements are used to characterize these nanorods. The XRD pattern show the tetragonal rutile and polycrystalline nature of SnO2 nanorods which is also confirmed by TEM. The TEM images exhibit that the diameter of SCC54 nanorods lie in the range of 15-20 nm, length~100-200 nm whereas for SFC54 specimen, diameter ~5-15 nm and length ~50-100 nm. In our previous work, we fabricated Co and Fe (3 and 5 mol% each) doped SnO2 nanoparticles which exhibited high ferromagnetism. It is observed that on Ce 3+ co-doping, nanoparticles assembled themselves into rod like structures and the values of saturation magnetization and dielectric properties have further enhanced. Thus the nature and the concentration of dopants are found to play crucial role in tuning the morphology, magnetic and electrical properties of nanostructures. The values of saturated magnetization (Ms) are 1.14 and 0.14 emu/g and coercive field are 112 and 42 Oe, in SCC54 and SFC54 specimen, respectively, at room temperature. The variation in dielectric behavior is attributed due to the interface polarization. However, in lower frequency regime, the decreasing trend of dielectric permittivity with increasing frequency is explained by the Maxwell-Wagner theory and Koops’ model, whereas, in higher frequency region, the resonant behavior is observed due to nano size effect.
