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Materials Science at Oregon State University

Electroceramic Materials

Date: Thursday, Nov 11th
Presenter: Narit Triamnak and Natthaphon Raengthon, OSU Materials Science


Narit Triamnak Abstract:

Electrical properties of Bi non-stoichiometry in 0.1 Bismuth-Zinc-Titanate/0.9 Barium Titanate perovskite ceramics

Many emerging technologies such as micro-flight or electric weapon system have electrical energy storage requirements that are not met by existing materials and devices. In our work, pseudo-cubic perovskite compositions based on the Bi(Zn1/2Ti1/2)O3-BaTiO3 and Bi(Zn1/2Ti1/2)O3-NaNbO3 systems show great promise for high energy density applications which exhibit permittivities over 1000 that persist to fields as high as 100 kV/cm. The high E-field properties are enabled by high densities in bulk ceramics and high insulation resistances. They also exhibit a slim and nearly linear dielectric response with no measurable remanent polarization, which may be an indication of weakly-coupled relaxor behavior. In this study, electrical properties of (Bi0.1+(x/100)Ba0.9)(Zn0.05Ti0.95)O3 solid solutions where x = -3,-2,...,3 have been investigated. It is expected that non-stoichiometry on the A-site might have a strong influence on the dielectric properties of this material.

Natthaphon Raengthon Abstract:

Dielectric Properties of (Ba,Bi0.2)(Zn,Ti)O3 Ceramics for High Temperature Applications

Lead-free perovskite BaTiO3-based ceramic have been embedded in a number of applications. An existence of high permittivity makes them useful for capacitor and other electronic applications. New ceramic capacitor that exists high and stable permittivity over a wide temperature range is needed in high-temperature electronics for example spacecraft, deep oil well industries, etc. Study of doped-BaTiO3 with various dopants such as Y2O3, MnO2, CaTiO3 and CoO showed improved temperature dependence of permittivity of material (for example, X7R, which exhibits 15% change of capacitance in temperature range of -55 to 125 °C). In this study, BaTiO3-Bi(Zn1/2Ti1/2)O3 ceramics showed promising properties for high-temperature applications. Compositions close to 0.8BaTiO3-0.2Bi(Zn1/2Ti1/2)O3 revealed pseudo-cubic symmetry and showed a linear dielectric response. The existence of a nearly flat temperature dependence of the relative permittivity over the temperature range 100 °C to 350 °C was also obtained. The effects of cation non-stoichiometry and doping were investigated in an attempt to optimize the insulation. The dielectric response of doped and undoped (Ba0.8-xBi0.2)(Zn0.1Ti0.9)O3 ceramics with x = 0, 0.02, 0.04, 0.06, and 0.08 were investigated. The optimum compositions exhibited high relative permittivity in excess of 1150 and low loss tangents (dielectric loss less than 0.03) that persist up to a temperature of 400 °C. The mechanism responsible for these unique dielectric properties will also be discussed.