Event Type:
MSE Grad Presentation
Date:
Talk Title:
The Impact of Sintering Temperatures, Humidity Levels, and Applied Pressures on the Dielectric Properties and Density of Alumina
Location:
J. Erskine Love Building Conference Room 210

Abstract

Alumina is one of the most common ceramic materials in our daily lives, offering many beneficial properties. It can function as a pure capacitor or an effective insulator, making the study of its electrical properties essential. This thesis investigates the dielectric properties, specifically impedance and permittivity, of both sintered and non-sintered alpha-alumina samples with different particle sizes ranging from nano to micron size range. For non-sintered specimens, the effects of varying compaction pressures from 100 MPa to 450 MPa were examined using the Carver Unheated Press to compress the powder into pellets. All five alumina specimens investigated exhibited clear RC behaviors with impedance decreasing with increasing applied pressure. However, some samples showed a noticeable rebound in the Nyquist impedance plot at certain pressure ranges. The Spark Plasma Sintering technique was employed to sinter the alumina powders into pellets. To better understand how sintering temperatures affect the dielectric properties of alumina, seven different temperatures ranging from 1000°C to 1300°C, with 50°C increments, were utilized. It was found that alumina specimens sintered below 1200°C are highly susceptible to ambient humidity even when their density was over 90%, whereas those sintered at or above 1200°C are resistant to humid environments. These trends were analyzed through comprehensive impedance and dielectric spectroscopy measurements as a function of frequency, humidity, and sintering temperature. This analysis revealed that specimens with lower bulk density exhibit lower dielectric permittivity at high frequencies than those with higher densities, but significant increases occur at frequencies below 105 Hz when exposed to humidity. A notable transition at 1150°C sintering temperature was also identified to be related to the difference in response for the low-density and high-density samples. Detailed structural and compositional analyses of these samples were conducted using X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and particle size analysis.

Committee

  • Professor Rosario A. Gerhardt - School of Materials science and Engineering
  • Professor Chaitanya S. Deo – School of Mechanical Engineering
  • Professor Blair K. Brettmann - School of Chemical and Biomolecular Engineering