Morphologically controlled dielectric dispersion and energy density optimization in Co/Ni spinel ferrites.

Precise control of morphology of functional materials, in particular when grown on nanoscale has revolutionized their physio-chemical characteristics for various applications. These nano-dimensional materials serve as basic building blocks for the development of new technological applications. Here in, we synthesized a series of nanorods and nano flakes of Co/Ni spinel ferrites using a hydrothermal method. NH 4 F as a surfactant, assisted to precisely control the morphology and dimension of nanostructures. The transformation of inverse spinel structure of cobalt ferrite to mixed spinel upon Ni substitution remarkably influenced their dielectric and ferroelectric response. The increase of dielectric response with Ni substitution was explained on the basis of Maxwell Wagner model. The impedance investigation probed the activation of different electro-active regions in different frequency range. Ferroelectric behavior along with energy density calculation provided a map to estimate the potential of functional nanostructures for energy storage applications. Magnetic properties were also obtained at room temperature showing high coercive hysteresis loops. [ABSTRACT FROM AUTHOR]