Thin Films And Sub-Micron Powders Of Complex Metal Oxides Prepared By Nebulized Spray Pyrolysis And Brillouin Scattering Investigations Of Phase Transitions In Solids
The thesis consists of two parts. Part 1 deals with the preparation of thin films and sub-micron powders of complex metal oxides by nebulized spray pyrolysis (NSP) and Part 2 consists of Brillouin scattering studies of solid materials exhibiting interesting phase transitions. The simple technique of NSP has been employed to prepare thin films of A12O3, PbTiO3, Pb(Zr0.5Ti0.5)O3 (PZT) and PbZrO3 on single crystal substrate. The films were characterized by various techniques for their composition, structure, morphology and dielectric properties. Ferroelectric (FE) films of the configuration FE/LaNiO3/SiO2/Si (FE = PbTiO3 and PZT), wherein the LaNiO3 barrier electrode was also deposited on the SiO2/Si substrate by NSP, have been investigated. The films exhibit satisfactory ferroelectric properties. PbZrO3 films deposited on LaNiO3/SiO2/Si substrates show good features, including a reversible AFE ↔ FE transition. Sub-micron particles of TiO2, ZrO2, Pb(Zr0.5Ti0.5)O3, Al2O3, S1O2 and mullite have been prepared by NSP and characterized by various techniques. Brillouin scattering has been used, for the first time, not only to characterize the Peierls transition but also the incommensurate to commensurate transition in the one-dimensional blue bronze, K0.3M0O3. The charge density wave transition in NbSe2 has also been investigated by Brillouin scattering. The charge ordering and antiferromag-netic transitions in single crystals of the rare earth manganates, Nd0.5Ca0.5MnO3 and Pr0.63Ca 0.37MnO3, have been investigated by Brillouin scattering. It is noteworthy that the temperature variation of the Brillouin shift and intensity parallel to that of the magnetization, thereby throwing light on magnetic excitations in charge-ordered state. Brillouin scattering investigations of C60 and C70 films have yielded values of the elastic moduli.