Engineering Commons^™

Impedance Spectroscopy Of Batio₃ Cubes Suspended In Lossy Liquids As A Physical Model Of Two-Phase System, Piotr Z. Jasinski, Vladimir Petrovsky, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Impedance spectroscopy techniques were used for analysis of the physical model in a two-phase system toward determining of dielectric constant of dielectric particles suspended in liquids at various solids loading (volume fraction) levels. Model experimental studies were conducted using BaTiO3 as a dielectric material that was prepared as small cubes of uniform size (2×2×1 mm). Barium titanate (BT) cubes having a dielectric constant of 3850 were immersed in liquids of low dielectric constant and moderate electrical conductivity. Measured impedance spectra consisted of two semicircles, which were fitted for (R∥C)(R∥C) equivalent circuit. The parameters obtained from fitting were compared with the …

Neodymium Oxide Doped Melt Textured Yba₂Cu₃O₇₋ₓ Single Crystals, Fatih Dogan, Stephen W. Sofie, Michael Strasik, Kevin E. Mccrary, Arthur C. Day, William C. Hicks

Materials Science and Engineering Faculty Research & Creative Works

Processing, microstructure and property relationships in neodymium oxide doped high temperature superconducting YBa₂Cu₃O_7-x (Y123) were investigated. It has been observed that a small amount (~ 0.25 - 1 mol%) of Nd₂O₃ results in the formation of nanosized secondary phases which may have a significant effect on the superconducting properties of melt textured Y123 single crystals. It was further observed that addition of Nd₂O₃ greater than 1 mol% leads to multiple nucleation during solidification of Y123 and results in polycrystalline samples. Melt textured single crystals of Y123 with < 1 mol% were successfully grown and characterized with respect to microstructural development and superconducting properties.

Electrical Properties Of Srbi₂Ta₂O₉ Ferroelectric Thin Films At Low Temperature, Pingxiong Yang, David L. Carroll, John Ballato, Robert W. Schwartz

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The temperature dependence of electrical properties for SrBi2Ta2O9 thin film capacitors with platinum electrodes (Pt/SBT/Pt) on silicon wafers was studied from 10 to 300 K. with a decrease in temperature from 300 to 200 K, the remanent polarization of the thin films shows about an 11% reduction from its 300 K value; however, it is reduced by about 87% reduction from its 200 K value when the temperature drops from 200 to 100 K. with a decrease to 200 K, the polarization fatigue was significant, and the capacitor shows an approximate 29% reduction in polarization from its initial value following …

High Energy Density Dielectrics For Symmetric Blumleins, Wayne Huebner, Shi C. Zhang

Materials Science and Engineering Faculty Research & Creative Works

Multilayer, tape cast ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>10⁶ J/m³) and physical size reduction. In particular, symmetric Blumleins are desired with the following properties:

• High voltage hold off (≥ 300 kV)
• High, nondispersive permittivity: ≈100 to 900
• Ability to be fabricated into various shapes and sizes
• Surface flashover inhibition at the edge
• Ability to be triggered by surface flashover switching

The compositions being pursued are based on pure BaTiO₃ dielectrics. Our approach is to add glass phase additions which result …

Grain Oriented Crystallization, Piezoelectric, And Pyroelectric Properties Of (Baxsr₂ - X)Tisi₂O₈ Glass Ceramics, Jianping Zhang, Burtrand I. Lee, Robert W. Schwartz, Zhenya Ding

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Polar, nonferroelectric (BaxSr2 - x)TiSi2O8 glass ceramics with highly oriented crystallites were prepared by a gradient temperature heat treatment technique. The crystallization mechanism and microstructures of (BaxSr2 - x)TiSi2O8 glass ceramics were investigated by means of differential thermal analysis, x-ray diffraction and scanning electron microscopy, and the dielectric, piezoelectric and pyroelectric properties were investigated for various compositions. The results show that polar (BaxSr2 - x)TiSi2O8 glass ceramics have a low dielectric constant and a high hydrostatic figure of merit dh × gh = ~ 2500. This high hydrostatic figure of merit, along with other unique characteristics, such as no aging …

Correlation Of Wettability And Interfacial Reaction To The Densification And Dielectric Properties Of Fluxed-Batio₃, Sea-Fue Wang, Wayne Huebner, Joseph P. Dougherty

Materials Science and Engineering Faculty Research & Creative Works

Reducing the sintering temperature of BaTiO3 has typically been achieved through the use of a fluxing agent to promote densification by liquid phase sintering. Liquid phase formation in these systems is due either to the melting of the flux or to the formation of a eutectic liquid between the flux and BaTiO3. In this paper, the correlation between the wettability and interfacial reactions between fluxes and BaTiO3 with respect to the densification behavior associated with liquid phase sintering, and the resulting dielectric properties is presented. Fluxes used in this study include 5ZnO*2B2O3, 5CdO*2SiO2, Pb5Ge3O11, CuO*TiO2, 3Bi2O3*B2O3, and LiF.

Evaluation Of Yba₂Cu₃O₇₋ₓ Bulk Superconductors For High Field Magnet Applications, Michael Strasik, Fatih Dogan, J. Liu, Mehmet Sarikaya, K. Y. Blohowiak, D. F. Garrigus, T. S. Luhman, Kevin E. Mccrary, I. A. Aksay, W. B. Hicks

Materials Science and Engineering Faculty Research & Creative Works

Processing of YBCO single crystals was carried out by solidification of semi-liquid YBCO composition using a seeding technique. Microstructural characterization of the pinning centers was investigated by transmission electron microscopy. Characterization of single crystals was carried out, relating grain size and shape to the corresponding flux profiles. Current densities were calculated based on measured trapped fields. Once circulating currents were established, flux pumping and quenching experiments were conducted. These large single crystals will be incorporated into electromagnetic forming devices for use in the military and commercial aircraft manufacturing and service industries.