Influence of oxygen octahedral tilting on the properties of low-dimensional lead-zirconium-titanate systems

In this thesis, we investigate low-dimensional Pb(Zr,Ti)O3 (PZT) systems in the presence of antiferrodistortive (AFD) oxygen octahedral tilting. In Chapter 1, some basic concepts and definitions useful for the following discussion are brought in. Chapter 2 addresses a question of AFD influence on epitaxial strain induced phase transitions in PZT ultrathin films under the short-circuit (SC) electrical boundary conditions, as a function of applied strain and alloy composition. Chapter 3 considers the same two-dimensional system under the open-circuit (OC) electrical boundary conditions leading to a formation of stripe domains. More precisely, properties of multi-domain system under the influence of AFD degrees of freedom using the Monte Carlo techniques are studied in Chapter 3. Chapter 4 deals with novel phenomena which appear in the zero-dimensional stress-free cubic nanodot made of PZT disordered solid solution under the OC electrical boundary conditions in the ground state. The consequences of coupling between the electric dipoles organized in vortices and AFD oxygen octahedral tilting is investigated and new order parameter to describe the new state of the system is introduced. In Chapter 5, the same zero-dimensional system under the SC conditions is examined which reveals the Curie temperature dependence on Ti content in the PZT alloy and the size of a nanodot enhanced by the influence of AFD displacements. Chapter 6 briefly lists the main achievements of the research discussed in the Thesis.