Synthesis, Structure, Optical, SHG and Multiferroic Investigations on Compounds derived from Mineral Structures

Abstract

The present thesis provides a systematic investigation of compounds derived from different mineral structures. The compounds were explored for their optical, visible light-activated photocatalysis, Second Harmonic Generation (SHG), and multiferroic behavior. The preface provides an appropriate foreword to the work described in the thesis. The thesis has eight chapters that include the preface and summary and future directions. Chapter 2 describes the development of new colored compounds based on the Garnet structure. The distorted tetrahedral geometry and possible metal-metal charge transfer (MMCT) transitions give rise to many new and brilliantly colored compounds that have been described. The optical studies on Corundum-derived compounds were described in Chapter 3. Here, the distorted octahedral coordination along with MMCT transitions helped in the development of new inorganic-colored compounds. The mineral Paganoite was explored in Chapter 4. In addition to developing new colored compounds, the Paganoite, BiCdVO5, and BiMgVO5 were also shown to be good candidates for visible light-activated photocatalysis. Photocatalytic C−C bond cleavage of alkenes and aerobic oxidation of alcohols was investigated with good yields and selectivity. The usefulness of non-centrosymmetry in the well-known stuffed Tridymite structure was explored in Chapter 5. The studies reveal many interesting-colored compounds that also exhibit multiferroic behavior. The observation of multiferroic behavior in these compounds is an important discovery. The studies of two closed related minerals, Dugganite and Langasite were described in Chapters 6 and 7. Both the structures stabilize in a non-centrosymmetric space group and exhibit good second harmonic generation (SHG) values. The Dugganite family of compounds also exhibits interesting new colors as well. The Langasite family of compounds was shown to exhibit white-light emission with minimal concentrations of rare-earth ions. The findings of the present investigation on various adaptable mineral structures provide possible directions for further growth towards developing new colored inorganic compounds, non-centrosymmetric oxides, and visible light-activated photocatalysis. The well-known structures of solid-state chemistry have been explored over many decades and the number and variety of mineral structures are far too many and the present thesis identifies a few of those structures. We believe that the present work opens the possibility of exploring many similar mineral structures in the future