Electronic Ceramics Development
Dielectrics, Thin Films, Electrospinning, Ceramic Foams, Devices

Current Projects

Project Title: Fundamental structure-dielectric property relationships of fluorite-related ceramics
Funding Agency: National Science Foundation
Contract Number: DMR-0449710

Anion-deficient fluorite-related crystal structures (A₂B₂O₇) can accommodate various cations, thus allowing their properties to be tailored. Ceramics with these structures have recently become attractive dielectrics. The present study is aimed to develop a paradigm for compositional design of fluorite-related ceramics with optimized dielectric properties and is currently investigated on the Ln₃NbO₇ and Ln₂(Ln’,Nb)O₇ ceramics. We have shown the dielectric relaxation occurs in the weberite-type Ln₃NbO₇ (Ln = La, Nd and Gd). Dielectric relaxation is commonly observed in pyrochlore and doped fluorite structures, but there are very few publications on weberite-related structures. Current effort is the understanding the nature of relaxation behavior.

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Project Title: Single Crystal Electroceramic Nanofibers by Electrospinning
Funding Agency: National Science Foundation CAREER
Contract Number: DMR-0449710

During the last years, several groups across the world have concentrated on the adaptation and further development of electrospinning (e-spinning) to enable ceramic fiber synthesis. Thus far, more than 20 ceramic systems have been synthesized as micro- and nanofibers. These fibers can be amorphous, polycrystalline, dense, porous, or hollow. This article reviews the experimental and theoretical basis of ceramic e-spinning. Furthermore, it introduces an expanded electro hydrodynamic (EHD) theory that allows the prediction of fired fiber diameter for lanthanum cuprate fibers. It is hypothesized that this expanded EHD theory is applicable to most ceramic e-spinning systems. Furthermore, electroceramic nanofibers produced via e-spinning are presented in detail along with an overview of electrospun ceramic fibers.

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Project Title: Piezoelectric Coefficient (d33) Characterization System (Lefki et al))
Funding Agency: Fundable Area
Contract Number:

Widely used electronics, when compared to organic based electronics are brittle, have difficult processing procedures, and are relatively costly. Roll processing allows for circuits to be printed directly on the flexible substrate like a conventional inkjet printer does on paper. For this technology, instead of paper, a spool of flexible substrate material can potentially be used. The origin of this technology is based on the plastic like properties that the polymers exhibit due to their flexible chain structure. Organic electronics also are light weight, and allow for more aesthetic applications involving electronic (flexible monitors). In addition to this technology is the incorporation of a piezoelectric material, upon mechanical strain, the energy is converted to electrical energy – altering the transistors properties. The technology has been tested to exhibit transistor qualities in Dr. Franky So’s Organic electronics laboratory in the UF Materials Science Department, guided by Dr. Juan C.Nino, and Dr. F.So.

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Project Title: Synthesis of Ceramic BaTiO₃-based Foams with Controlled Micro- and Mesostructure
Funding Agency: Fundable Area
Contract Number:

Ceramic foams are of significant technological interest as they offer favorable properties including low density, low thermal conductivity, variable mechanical strength, high thermal shock resistance and high surface area. Although focused research on cellular ceramics has been going for at least three decades, to date there has been little investigation on electroceramic foams. BaTiO₃ foams were synthesized via direct foaming method. In order to control the microstructure and by extension the properties, synthesis parameters such as foaming agent, composition, sintering time, and sintering temperature were varied to determine their influence. The effect of each parameter on the microstructure was measured and characterized using scanning electron microscopy, image analysis, density measurements, and mercury porosimetry. Microstructure was classified in terms of strut stability, average grain size, average pore size, porosity, and grain boundary integrity. For example, foams with 30% ceramic volume were synthesized using a laboratory developed polyurethane system and a commercial silicon-free polyurethane system. When sintered at 1400 °C for 8 hours they produced stable struts and uniform pore-size distributions. The laboratory foam had a porosity of 67 %, an average grain size of 44.4 µm and an average pore size of 66.7 µm. The commercial silicon-free foam had a porosity of 73 %, an average grain size of 20 µm and an average pore size of 99 µm. The synthesized foams have potential mechanical and electrical applications.

SEM Image of BaTiO₃ foam: foamed with the University of Rome polyurethane system and sintered for 8 hours at 1400^oC.

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Project Title: Solvothermal Synthesis of SrTiO₃ Compounds for Thermoelectric Applications
Funding Agency: Fundable Area
Contract Number:

Thermal energy conversion is a prime example of a renewable energy resource that is available from many sources. Central to these sources are thermoelectric materials because they can yield an electrical current in response to a thermal gradient. The primary need in the design of thermoelectric materials is an enhancement of the energy conversion efficiency through optimizing materials and properties associated with the energy conversion process.

Current investigation explores and analyzes the properties of textured ceramics of layered Ruddlesden-Popper oxides. Research specifically focuses on the influence of the distribution of grain orientations on the transport anisotropies. Since Ruddlesden-Popper compounds are stochiometrically layered, they provide an ideal platform to investigate the effect of crystallographic anisotropy on material properties. Because of this property, strontium titanate (SrTiO₃) along with other versions of the compound (Sr_x+1Ti_xO_3x+1 | x=1,2,3) will serve as a model system to investigate structure-property relationships in oxide thermoelectrics.

To synthesize platelet-shaped particles to be used in texture processing, a solvothermal process will be used. Thermal and electrical conductivities will be measured in order to establish various texture-anisotropy relationships. It is expected that the properties related to the layered structure of Sr_x+1Ti_xO_3x+1 compounds will lead to a large degree of anisotropy in textured ceramics, revealing the enhancement of certain properties at the expense of directional preference.

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Project Title: Hybrid Organic-Electroceramic Devices for Smart Electronic Applications
Funding Agency: Fundable Area
Contract Number:

A conventional ultrasonic imaging system includes two elements: 1) an element that generates acoustic waves, and 2) a sensor that detects the reflected signals. In a typical ultrasonic imaging procedure, a probe is manually scanned across the imaging area. This procedure can be tedious and time consuming, and often the image quality is poor.

This project involves creating a piezoelectric device structure for improved acoustic wave sensing. This is accomplished by building the device using different materials for different components. The piezoelectric thin film field effect transducer can be a thin film transistor (TFT) with either a piezoelectric film gate or a composite gate having a dielectric film and a piezoelectric film. The TFT structure can be either a top gate device or a bottom gate device. In an embodiment, the piezoelectric device structure can be used to form an array of piezoelectric thin film field effect transducer. A TFT switch can drive each piezoelectric transducer in the array. The piezoelectric transducer can both generate and sense acoustic waves. In a sensing mode, a signal from an acoustic wave can be collected at a readout terminal of the piezoelectric transducer. In a generating mode, an excitation signal can be applied across the piezoelectric transducer while the switch is ‘on’.