Devices with nano-crystalline microstructures have been shown to possess improved electrical properties. Further advantages include lower processing temperatures; however, device fabrication from nano-particles poses several challenges. This presentation describes a novel aqueous synthesis technique to produce large batch sizes with minimal waste. The precipitate is readily converted at less than 550 C to a phase pure, nano-crystalline Pb{sub 0.88} La{sub 0.12}(Zr{sub 0.70} Ti{sub 0.30}){sub 0.97} O{sub 3} powder. Complications and solutions to sample fabrication from nano-powders are discussed, including the use of glass sintering aids to improve density and further lower sintering temperatures. Finally, electrical properties are presented to demonstrate the potential benefits of nano-crystalline capacitors.
Attractive for numerous technological applications, ferroelectronic oxides constitute an important class of multifunctional compounds. Intense experimental efforts have been made recently in synthesizing, processing and understanding ferroelectric nanostructures. This work will present the systematic characterization and optimization of barium titanate and lead lanthanum zirconate titanate nanoparticle based ceramics. The nanoparticles have been synthesized using several solution and pH-based synthesis processing routes and employed to fabricate polycrystalline ceramic and nanocomposite based components. The dielectric and ferroelectric properties of these various components have been gauged by impedance analysis and electromechanical response and will be discussed.
Nano-materials have shown unique crystallite-dependent properties that present distinct advantages for dielectric applications. PLZT is an excellent dielectric material used in several applications and may benefit crystallite engineering; however complex systems such as PLZT require well-controlled synthesis techniques. An aqueous based synthesis route has been developed, using standard precursor chemicals and scalable techniques to produce large batch sizes. The synthesis will be briefly covered, followed by a more in-depth discussion of incorporating nanocrystalline PLZT into a working device. Initial electrical properties will be presented illustrating the potential benefits and associated difficulties of working with PLZT nano-materials.
Structural phase transformations between ferroelectric (FE), antiferroelectric (AFE), and paraelectric (FE) phases are frequently observed in the zirconia-rich phase region on the lead zirconate-titanate (PZT) phase diagram. Since the free energy difference among these phases is small, phase transformation can be easily induced by temperature, pressure and electric field. These induced transformation characteristics have been used for many practical applications. This study focuses on a hydrostatic pressure induced FE-to-AFE phase transformation in a tin modified PZT ceramic (PSZT). The relative phase stability between FE and AFE phases is determined by the dielectric permittivity measurement as a function of temperature from -60 C to 125 C. A pressure-temperature phase diagram for the PSZT system will be presented.
Phase transformation between the ferroelectric (FE) and the antiferroelectric (AFE) phases in tin modified lead zirconate titanate (PSZT) ceramics can be influenced by pressure and electric field. Increasing the pressure has the tendency to favor the AFE phase while electric field favors the FE phase. In this study, these phase transformations are studied as functions of external pressure, temperature, and dc bias. The shifting of transformation temperature and the relative phase stability between FE and AFE with respect to these external parameters will be presented. Results will be compared to a pressure-induced depoling behavior (or FE-to-AFE phase transformation) for the PSZT ceramic. Fundamental issues relates to the relative phase stability will be discussed from the perspective of lattice dynamics theory.
The ceramic nanocomposite capacitor goals are: (1) more than double energy density of ceramic capacitors (cutting size and weight by more than half); (2) potential cost reductino (factor of >4) due to decreased sintering temperature (allowing the use of lower cost electrode materials such as 70/30 Ag/Pd); and (3) lower sintering temperature will allow co-firing with other electrical components.
This late start RTBF project started the development of barium titanate (BTO)/glass nanocomposite capacitors for future and emerging energy storage applications. The long term goal of this work is to decrease the size, weight, and cost of ceramic capacitors while increasing their reliability. Ceramic-based nanocomposites have the potential to yield materials with enhanced permittivity, breakdown strength (BDS), and reduced strain, which can increase the energy density of capacitors and increase their shot life. Composites of BTO in glass will limit grain growth during device fabrication (preserving nanoparticle grain size and enhanced properties), resulting in devices with improved density, permittivity, BDS, and shot life. BTO will eliminate the issues associated with Pb toxicity and volatility as well as the variation in energy storage vs. temperature of PZT based devices. During the last six months of FY09 this work focused on developing syntheses for BTO nanoparticles and firing profiles for sintering BTO/glass composite capacitors.