The aim of this research is to develop a fundamental understanding of the dominant defect species and the relevant defect equilibrium conditions for bismuth-containing perovskites to help guide the development of these materials for emerging applications. This is of paramount importance for many demanding applications, because ultimately the defect equilibria...
Lead-free ceramics of composition Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ were prepared
using solid state synthesis techniques. The dielectric spectra showed a Tmax of more than 320 °C
for all compositions, and the transitions became increasingly diffuse as the Bi(Mg₁/₂Ti₁/₂)O₃
content increased. A lower temperature transition, indicating a transformation from an ergodic to a
non-ergodic...
Lead-free Bi(Mg₁/₂Ti₁/₂)O₃-(Bi₁/₂K₁/₂)TiO₃-(Bi₁/₂Na₁/₂)TiO₃ (BMT-BKT-BNT) ceramics have
been shown to exhibit large electromechanical strains under high electric fields along with
negligible fatigue under strong electric fields. To investigate the role of point defects on the
fatigue characteristics, the composition 5BMT-40BKT-55BNT was doped to incorporate acceptor and
donor defects on the A and...
The need for miniaturization without compromising cost and performance continues to motivate research in advanced capacitor devices. In this report, multilayer ceramic capacitors based on relaxor BaTiO₃-Bi(Zn₁/₂Ti₁/₂)O₃ (BT-BZT) were fabricated and characterized. In bulk ceramic embodiments, BT-BZT has been shown to exhibit relative permittivities greater than 1000, high resistivities (ρ > 1...
Sensors find a variety of applications in portable electronics, automotive and biomedical solutions. The demand for low power and high dynamic range makes the design of digital sensor readout circuits quite challenging. Traditionally, these circuits are realized using amplifiers with passive feedback or precision analog comparators which are power hungry...
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...
The properties of (1-x)BaTiO3-xBi(Mg1/2Ti1/2)O3 (BT-BMT) ceramics were fabricated from reagent-grade ceramic powders by solid-state methods and investigated for solubility, relative permittivity, dielectric loss, polarization, and electromechanical strain. The solubility limit was found to be between x = 0.3 and 0.4. Ba-deficient samples were fabricated, corresponding to stable single-phase compositions; these...
The ternary system (Bi₀.₅Na₀.₅)TiO₃-(Bi₀.₅K₀.₅)TiO₃-Bi(Mg₀.₅Ti₀.₅)O₃ (BNT-BKT-BMgT) was explored along the [75-(x 2) ]Bi₀.₅Na₀.₅TiO₃ - [25-(x 2)]Bi₀.₅K₀.₅TiO₃ - [x]Bi(Mg₀.₅Ti₀.₅)O₃ composition line. Thin films were fabricated using chelated mixing route solutions spin cast onto platinized silicon substrates. Processing parameters such as: excess cation molar%, solution molality, and crystallization temperatures, for composition where x=0,...
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...
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...
Narratives are central to communication and the human experience. For a computer system to understand a narrative, it must be able to identify the key facts or plot elements that describe what happened or how the world has changed. These element are called events;establishing a document’s events and the relationships...
We explore the application of deep learning to the disparate fields of natural language processing and computational biology. Both the sentences uttered by humans as well as the RNA and protein sequences found within the cells of their bodies can be considered formal languages in computer science, as sets of...
This dissertation addresses object recognition in challenging settings, where distinct object classes are visually very similar (e.g., species of birds and insects) and/or access to training examples of object classes is limited (e.g., due to the associated high costs of data annotation). In this dissertation, we present a variety of...
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...
This work investigates the effect of cation substitution on the properties of the lead-free, solid solution (Na₀.₅Bi₀.₅)TiO₃-BaTiO₃ (NBT-BT). Substitution into NBT-BT increases disorder and increases the relaxor ferroelectric properties. These relaxor ferroelectric materials show large piezoelectric strains that can be utilized in actuator applications. Ceramic samples were prepared using standard...
Analysis of observations on sequential events over time is common in real life. Sequential measurements over time describing the behavior of systems are usually called time series data, which have been collected in a wide range of disciplines. Over the years there have been multiple research areas in studying stochastic...
Two perovskite materials (Bi0.5(A)0.5)(Sc0.5Nb0.5)O3, where A = K+ and Na+ were synthesized phase pure for the first time. Their structures were determined by indexing synchrotron X-ray diffraction data and subsequent combined Rietveld refinement on neutron and synchrotron X-ray diffraction data revealing significant disorder on the A-sites of these materials. A...
Emergence of highly accurate Convolutional Neural Networks (CNNs) with the capability to process large datasets, has led to their popularity in many applications, including safety/security-sensitive (e.g. disease recognition, self-driving cars). Despite the high accuracy of convolutional neural networks, they have been found to be susceptible to adversarial noise added to...
The role of A-site non-stoichiometry was investigated in lead-free piezoelectric ceramics based on compositions in the 1-x(Bi₀.₅Na₀.₅TiO₃)-xBaTiO₃ system near the morphotropic phase boundary where x = 0.055, 0.06 and 0.07. The samples were prepared by a conventional solid state mixed oxide route with the A- site stoichiometry modified to incorporate...
In weak supervision learning, label information can be provided at different levels of granularity. For example, in multi-instance multi-label learning, samples are organized into bags and labels for each class are provided at the bag level. For small datasets, this approach offers means of reducing the labeling efforts. However, in...
This dissertation demonstrated that the electrical properties of complex oxide-based perovskite materials could be controlled through the careful modification of both material composition and structure. This was first shown through the modification of lead zirconate titanate (Pb(Zr0.52Ti0.48)O3, PZT) solid solutions with bismuth indate (BiInO3, BI) where the relative stability of...
Natural Language Comprehension is a challenging domain of Natural Language Processing. To improve a model’s language comprehension/understanding, one approach would be to enrich the structure of the model to enhance its capability in learning the latent rules of the language.
In this dissertation, we will first introduce several deep models...