Partha Hajra

Magnetodielectric effect in Ni0∙5Zn0∙5Fe2O4–BaTiO3 nanocomposites

Composites comprising of nanoparticles of Ni0∙5Zn0∙5Fe2O4 (NZF) and BaTiO3 (BT), respectively were synthesized by a chemical method. The particles had diameters in the range of 15–31 nm. NZF was prepared by a coprecipitation technique. This was soaked in a sol containing BT. Compositions synthesized were xNZF-(1 – x) BT, where x = 0∙7, 0∙5 and 0∙3, respectively. The composites showed ferromagnetic hysteresis loops due to NZF phase. The analysis of coercivity variation as a function of temperature gave blocking temperatures in the range of 306–384 K depending on the diameter of the ferrite nanoparticles. This implied that superparamagnetic interactions are above these temperatures. The nanocomposites also exhibited ferroelectric behaviour arising due to the presence of BT. The remanent polarization of the samples was small. This was adduced to the nanosize of BT. The specimens showed magneto-dielectric (MD) effect in the magnetic field range 0–0∙7 Tesla. The MD parameter measured at the maximum magnetic field was around 2%. This was one order of magnitude higher than that reported so far in similar composite systems. This was explained on the basis of a two-phase inhomogeneous medium model with an interface between them, the phases possessing drastically different electrical conductivities.

Nanoindentation studies on composites of CuO nanoparticles-lithia silica nanoglass

Nanoindentation of CuO-lithia silica nanoglass (CuO-NG) composite was studied and compared with only CuO nanoparticles (CuO). Youngs Modulus (E) and hardness (H) of the composite was found to be greater in comparison with CuO nanoparticles. Creep measurements showed that Creep strain rate (CSR) is lower for composite material than only CuO. This is due to decrease of copper diffusion through nanoglass phase in composite sample.