To study the effect of morphology on the optical, magnetic and electrical properties of some nanostructured transition metal oxides

Abstract

In this thesis work, different morphologies of nanosize nickel oxide (NiO) and its higher oxidation state (Ni2O3) have been successfully synthesized by facile hydrothermal process followed by calcination and chemical route. The main motivation of this work is to investigate the effect of morphology on magnetic, electrochemical capacitive, I-V characteristic, dielectric and photocatalytic behaviour. The coral-like NiO shows spin-glass like behaviour and asymmetric hysteresis loop at room temperature and also evidences that the microstructure could be helpful for developing magnetization based memory devices due to its high barrier height. Coral-like and flake-like NiO have been used to investigate the electrochemical capacitive performance. Coral-like NiO contains less surface area, but it shows higher superoxide generation and better pseudocapacitive property. This new concept has developed to prepare efficient nanostructured photocatalyst and pseudocapacitive electrode materials for better electrochemical energy storage performance for next generation. In another work the I-V characteristic of coral and flake- like Ni2O3 has been studied in terms of metal-semiconductor junction device. These two devices perform in ultralow turn-on voltages, potential barrier and very ideal thermionic current. This has been first time examined that the charge transport across the junction follows non-adiabatic process rather than adiabatic character, which is much suitable for opto-electronic applications. The influence of particle size on frequency dependent dielectric properties of Ni2O3 has been studied at room temperature. This studies show that the grain and grain boundary play an important role for ac conductivity. The high values of εʹ and low loss clearly suggest that this material is highly desirable for power systems in advance electronics. It has also been observed that the degradation efficiency is pH dependent and has been obtained as 99.2% and 97.4% for CR and MB respectively for 1 hour. The catalyst is also found to be highly stable and re-usable with an average deviation of 0.79% and 0.67% respectively for CR and MB. This catalyst has enough potential to efficiently degrade CR and MB at a fast rate to their non-toxic forms.