Multifunctional Oxides Obtained by PLD: Applications as Ferroelectric and Piezoelectric Materials

Abstract

In this chapter we provide an overview of the results obtained on both lead based and lead free ferroelectric thin films deposited by PLD, in relation with the actual scientific and economic tendencies. There is an increasing trend to replace or to reduce the use of toxic elements such as lead, but there is no obvious complete solution for this problem, both types of multifunctional oxides having attractive properties. The perovskite materials, ABO3 oxides, environmental-friendly or not, will continue to be studied and their properties enhanced through different methods. Moreover, based on these properties (piezoeletric, ferroelectric, transport, optical or magnetic), new functionalities of the material can be added or modified with the help of material nanostructuring techniques. Properties of lead based oxides thin films such as PLZT and PMN-PT were investigated. PLZT thin films with different compositions have interesting dielectric and electro-optic behaviour. The effect of self-polarization in thin PMN-PT relaxor films could be of interest for pyrosensors and other applications based on the pyroelectric effect. As regarding the lead-free oxide materials, the obtaining and the characterisation of SBN and NBT-BT thin films will be presented. For the SBN thin films, the resulting value of the electro-optic coefficient r eff was calculated to be higher than the values reported for LiNbO3. Having a rather high Curie temperature, of 128 °C, compared to the higher Sr content compositions, the SBN:50 thin films can be potentially used in electro-optic devices operating near room temperature. Solid-solution systems (1−x)NBT-xBT based on Na0.5Bi0.5TiO3 (NBT) and BaTiO3 (BT) were investigated: for compositions situated at the morphotropic phase boundary between rhombohedral and tetragonal phase, high piezoelectric coefficient values and huge electric field-induced strain have been obtained.