Materials based on BiMO₃-modified BaTiO₃ have been shown to exhibit a number of attractive electrical and electromechanical properties. In addition, many of the materials in this broad family exhibit reduced sintering temperatures for densification as compared to pure BaTiO₃. We report here a study of the phase evolution and sintering...
The long-term goal of the research project initiated with this thesis is the development of lead-free, fully-transparent ferroelectric devices, such as ferroelectric capacitors or ferroelectric-gate field-effect transistors. Ferroelectric materials exhibit spontaneous polarization with the application of an external electric field, which is persistent upon removal of the applied field, and...
Lead zirconate titanate (PZT) is the dominant ferroelectric material in the market due to its excellent piezoelectric properties, relatively high Curie transition temperature (T[subscript C]), low cost, etc. However, because of emerging applications with requirements for high temperature (T[subscript C] > 400 °C) ferroelectrics, researchers are increasingly looking at alternative...
It has been well established that ferroelectric to relaxor crossover in piezoelectric ceramics exhibit promising electromechanical and dielectric properties over a wide temperature range, applying sensors and actuators transducers and such. A plethora of research has reported giant strain in various lead-free piezoelectric ceramics and attributed the reasoning to the...
Since its discovery, the anomalous dielectric behavior of CaCu₃Ti₄O₁₂ (CCTO)
has drawn a great deal of attention for many possible applications in electronic
devices. The origin of the giant dielectric constant in CCTO was explained via an
internal barrier layer capacitor model, and it has been reported that the dielectric...
High performance dielectric materials are needed for high power SiC- or GaN-based electronics which combine the best features of high energy density, low dielectric loss and high reliability and for advanced high-speed and high-voltage energy storage where temperature stability plays an important role in material properties. An ideal capacitor for...
We developed a model to investigate the dielectric properties of the
BaTiO₃ − Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) solid solution, which is a relaxor ferroelectric and exhibits long range disorder. The model uses ab initio methods
to determine all polarization states for every atomic configuration of 2 x 2 x 2
supercells of...
Solid solutions based on the perovskite ferroelectrics Bi₀.₅Na₀.₅TiO₃ (BNT) and Bi₀.₅K₀.₅TiO₃ (BKT) might someday replace current Pb-based ferroelectric and piezoelectric devices. This is one goal of the Restrictions on Hazardous Substances (RoHS) guidelines seeking to limit Pb in consumer devices. Although the Bi-based ferroelectrics are well suited to the task...
Relaxor characteristic of the solid solution (1-x)BaTiO₃-(x)Bi(Zn₁/₂Ti₁/₂)O₃ (BTBZT) was investigated in this research. X-ray diffraction technique and Raman spectroscopy revealed the crystal structure of BT-BZT at various compositions. For compositions with x ≤ 0.08, the solid solutions exhibited clear tetragonal symmetry and transitioned to pseudo-cubic symmetry as the content of...
Structure-property relationships in ferroelectrics extend over several length scales from the individual unit cell to the macroscopic device, and with dynamics spanning a broad temporal domain. Characterizing the multi-scale structural origin of electric field-induced polarization reversal and strain in ferroelectrics is an ongoing challenge that so far has obscured its...