| Smart materials are playing an increasingly important role in our ever-evolving technology because they can fulfill a multi-dimensional role in the development of smaller, cheaper and more effective devices. Future advances in the design and development of new applications heavily relies on our fundamental understanding of the behaviour of their constituting materials. Transparent solid solutions of Lead Lanthanum Zirconate Titanate (PLZT) ceramics were synthesised in the early 1970s and they have shown a great potential for practical applications mainly due to their strong piezoelectric and electro-optic properties. Even though many devices utilizing PLZT ceramics have been developed over the years, this polyvalent material has yet to be understood fully and, subsequently, exploited to its full potential. In this work, the fundamental dielectric properties of bulk PLZT ceramics, with compositions that exhibit a relaxor-type behaviour, have been investigated as a function of temperature, frequency and do electric fields. The piezoelectric and electrostrictive properties of the same samples were also measured at various harmonics as a function of superposed ac and do electric fields using a state-of-the-art laser interferometer. A theoretical model was fitted to the measured results and the dielectric and electromechanical material coefficients of the studied PLZT samples were found. Moreover, the electric field and thermal dependences of the refractive index of the same bulk PLZT samples were measured using a Fabry-Perot interferometric technique. Thin films made from various relaxor PLZT compositions were subsequently investigated as light waveguides, and the modal resonance of light inside these films was used to calculate their refractive index thermal coefficients and to enhance their electro-optic modulation behaviour. As in all ferroelectric materials, strong non-linearities in the PLZT properties became evident; these non-linearities were explained in terms of the crystalline phase transitions. Overall, this work not only contributed to the advancement of our understanding of relaxor PLZT ceramics, but also, new experimental techniques were developed and could be useful for future characterization of other ferroelectric materials.;Key Words: Relaxor Ferroelectrics, PLZT, dielectric, piezoelectric, electro-optic properties, thin film waveguides. |
