The Rationale for Colonialism: Akbar’s Dream (Notes)

Akbar’s Dream [1892] is among the last poems of Alfred, Lord Tennyson – Poet-Laureate of Britain. It was composed when the British Empire was at its apex of territorial expansion and Queen Victoria was the Empress of India. It is reflective of the position of Tennyson as PoetLaureate – whose ‘official’ task was to celebrate the achievements and other notable events of Britain. Tennyson was an ultra-conservative person who believed that Britain was doing a favour to the peoples they had conquered and subjugated. This was intended for their benefit so as to advance them in the scale of civilization.

Correlation of Crystal Structure and Dielectric Characteristics of Pyrochlore Based Oxides

Rare earth-based materials with pyrochlore structure have shown a potential for practical applications due to their stable crystal structure with tunable lattice parameters. Pyrochlore structure-based compounds have shown valuable interest in practical applications because of their structure tunability and stability. In this context, the stability of pyrochlore structure in a particular phase is quite essential for practical optimization of valuable dielectric, impedance and other multifunctional characteristics of rare-earth pyrochlores. This work contains a successful synthesis of pure phase pyrochlore based compounds including zirconates and niobates, with A and B-site substitution to determine their structural tunability and its effects on dielectric and other multifunctional properties. These rare-earth based pyrochlores not only show practically viable dielectric characteristics but also have significant ferroelectric and magnetic features. Most of the pyrochlores show disordered magnetic structure and have not been investigated properly yet. In this context, following detailed study of these thermally stable pyrochlores has been accomplished for their practical applications. A wet chemical sol-gel technique was utilized to synthesize pure phase pyrochlores. This method was found feasible, energy efficient and cost effective. Diffraction studies using X-rays revealed their stable pyrochlore structure with Fd ̅m space group. Structural tunability through A and B-site substitution was confirmed through Rietveld refinement. Perfect fitting and low residual factors from refinement prove the synthesis of pure phase pyrochlores. Calcination temperature of 1200 °C for 1 h was found to be the most favorable condition for the synthesis of these highly complex metal oxides. Field emission scanning electron microscopy operated in different operating modes at several voltages has confirmed the growth of nanoparticles with substitution, promoting the densification of the prepared ceramics. This densification led us to study the energy storage capability of these materials as they have already shown good ferroelectric properties. To check the variation in recoverable energy density of the material under consideration, the charge-discharge curves were plotted at different field strengths to study the recoverable energy density, energy loss density and energy storage efficiency as a function of applied field. Furthermore, magnetic properties of these pyrochlores were determined through vibrating sample magnetometer. Superparamagnetic effect was found in these pyrochlores with reasonably good magnetic susceptibility and small coercive fields. In addition, the variation in magnetic properties was also related to the particle size which showed that the maximum magnetization increases with decrease in particle size. Lastly, the magneto-dielectric study has been performed. The study of relative change in dielectric properties of the material with change in external magnetic field is called magneto-dielectric analysis. This analysis is actually the investigation of coupling between the magnetic properties of the material with its dielectric characteristics. Magneto-dielectric analysis exposed that dielectric behavior of the samples is influenced inversely with the application of external magnetic field. Negative behavior of magneto-dielectric coefficient can be understood on the basis of application of external magnetic field randomizes the electric dipoles present in the material which usually follow the external applied electric field. This study was also explained on the basis of Maxwell-Wagner‟s model.