Oxide Ion Conductivity of Mechanically produced Calcia Stabilised Zirconia for Oxygen Sensing Applications

Abstract

Cryo-milling was used to make calcia stabilized zirconia (CSZ) powders with 9 mol%, 12 mol%, and 15 mol% of calcia. Powder X-ray diffraction was done to examine the phase growth in prepared powders over the course of 80h of mechanical alloying (MA) in cryogenic environment at 300rpm. The calcined powders were hydraulically pressed into cylindrical shaped sensor elements in a uniaxial press and then sintered for 4h at 1400°C. The microstructure of sintered pellets were studied using Scanning Electron Microscope (SEM). Electrical Conductivity measurements of the prepared stabilized zirconia at various temperatures over a temperature range of 200°C to 500°C using a dual-probe impedance analyzer is carried out and the effects of composition and temperature on the grain boundary impedance of CSZ were analyzed. Conductivity is discussed in terms of ionic vacancies in the bulk due to calcium ion substitution and available grain boundary paths. Ionic Conductivity of prepared CSZ is compared for suitability in oxygen sensing applications.

Keywords:
Calcia-Stabilized Zirconia; Conductivity; Mechanical Alloying; Cryo-Milling