Electro-optic (EO) materials allow for the precise control of light using electrical signals, which has allowed for the advancement of an incredible array of photonic technologies such as laser systems and optical telecommunications. Most EO devices currently utilize single crystals, but high performance EO single crystals often have composition limitations since dopants can segregate and not all compositions can be grown using equilibrium restricted techniques. Bulk polycrystalline ceramic materials can potentially overcome such limitations and allow for the exploration of new EO systems. Due to the specific microstructures required for transparency, conventional processing techniques have difficulty in producing bulk polycrystalline EO ceramics. Reported here for the first time are the optical and EO properties of a new class of transparent lead free ceramic that outperforms EO materials in use today. This material is a barium titanate (BaTiO3) based solid solution, (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7 Ca0.3)TiO3 referred to here as BXT. The EO material was successfully processed using the Current Activated Pressure Assisted Densification (CAPAD) technique, commonly called Spark Plasma Sintering (SPS), which has been shown to be effective at consolidating optical materials. Using this technique along with a new powder synthesis method, it was possible to produce a transparent EO BXT ceramic with a highly dense and homogeneously reacted microstructure. Densified BXT shows a remarkable EO coefficient of 530 pm/V, which is superior not only to state of the art LiNbO3 crystals but also top-quality lead containing ferroelectric ceramics such as PLZT. This exceptional coefficient will allow for miniaturized EO systems with reduced operating voltages. The mechanisms behind the high EO performance in BXT were determined using additional EO and ferroelectric measurements. These measurements indicate that BXT undergoes a field induced structural evolution which heavily contributes to the EO effect. Along with efficient domain motion, this structural evolution includes a field induced phase change to a lower symmetry crystal structure. This work shows that lead free EO polycrystalline ceramics can have properties that are competitive or superior to state of the art EO materials. Due to its exceptional EO properties, BXT in particular has a promising future as an EO material.

Current Activated Pressure Assisted Densification (CAPAD) has emerged as one of the most promising methods of materials processing in recent years. This process involves the use of large currents to generate heat coupled with applied pressure in what has proven to be a very powerful powder consolidation technique. Despite intensive research, there is still much to learn about the intricacies of how this process works. In the first part of this work, three material systems, yttria stabilized zirconia, Si, and Al, were processed using the CAPAD technique in order to see how processing conditions affect the densification rates in the CAPAD process. It was found that all materials show a peak densification rate at a particular homologous temperature, which is discussed in terms of material bond type. Pressure was found to directly affect the magnitude of the maximum densification rate in all samples. In the second part of this study, a model was developed to estimate the density-temperature relationship in the CAPAD process. This model is dependent on two parameters that are linked to physical quantities. Experimental data for oxide ceramic materials was used to demonstrate the fitting capability of the model. Oxides were chosen because of the abundance of experimental data available in the literature. Estimating the dominant parameter can be done by finding a material system's activation energy for diffusion and comparing it to other known materials. Guidelines were given on how future CAPAD workers can use the model to save time and resources.

The number of youth incarcerated in Los Angeles (L.A.) has declined over the past several years, however the significance of this decline is uncertain. As the number of incarcerated youth in Los Angeles decreases, there has been a simultaneous increase in the proportion of youth arrested that are charged with violent crimes. At the same time, recidivism is high among California youth. Given this information, the downward trend in youth incarceration may be driven by changes in the policing of non-violent crimes rather than changes in the policing of all youth. Additionally, incarcerating youth may further promote violent crime instead of deterring it. In order to confirm or refute these implications, it is necessary to fully understand the relationship between youth incarceration and re-arrest for violent crime.

To date, there have been numerous studies that examine the effects of youth incarceration on recidivism, mental health and long-term socio-economic outcomes, but relatively few studies that assess the impact of youth incarceration on violent behavior and re-arrest for violent crime specifically. This study aims to expand our understanding of the impact of youth incarceration on behavior and re-arrest for violent crime with a focus on race and racism. I use a mixed-methods approach to answer questions about youth arrests, the experience of incarceration and recidivism among male youth in L.A. I analyze arrest data from the L.A. Police Department to assess the risk of re-arrest for violent crime and conduct interviews with L.A. County Probation officers, who oversee the care of male youth in detention, in order to understand the aspects of incarceration that impact youth behavior. Results from this research have the potential to inform future studies on the relationship between youth incarceration and recidivism, as well as contribute to a broader understanding about violence prevention strategies for high-need youth.