Preparation Protocol and Properties of YSZ Ceramic Electrolytes for Solid Oxide Cells

Electrolytes utilized in solid oxide cells (SOCs) are based on oxide ion-conductive ceramic materials. The conductivity occurs via oxygen vacancies in the crystal lattice, which are created by the introduction of dopant into the material. Fast and simple preparation of electrolytes using variable dopant content is of great importance for SOCs development. ZrO2 doped by Y2O3 (YSZ) is still considered to be a state-of-the-art material due to its conductivity and thermomechanical compatibility with electrodes. Therefore, a detailed procedure to fabricate YSZ electrolytes with desired dopant content is of significant importance. Each prepared electrolyte was examined by means of spectroscopic methods in combination with electrochemical ones. The results obtained allows to understand connection between electrolyte composition and structural properties.

Oxygen Sensors for Industrial Application

The present work aimed to study a family of solid ceramic electrolytes based on magnesium oxide doped zirconium oxide, usually identified as Mg-PSZ (zirconia partially stabilized with magnesia), used in the manufacture of oxygen sensors for molten metals. A set of electrolytes was prepared by mechanical (milling) and thermal (sintering) processing, varying the composition in magnesia and the cooling rate from the sintering temperature. These two parameters are essential in terms of phase composition and microstructure of Mg-PSZ, determining the behavior of these materials. The structural and microstructural characterization was done by means of X-ray diffraction (XRD). The electrical properties were analyzed by impedance spectroscopy in air. In general, the results obtained from various concentrations of dopant, different cooling rates and the same sintering step condition showed an increased conductivity for samples with predominance of high temperature stable phases (tetragonal and cubic).

Ionic and Thermal Transport in Na-Ion-Conducting Ceramic Electrolytes

We have studied the ionic and thermal transport properties along with the thermodynamic key properties of a Na-ion-conducting phosphate ceramic. The system Na1+xAlxTi2−x(PO4)3 (NATP) with x = 0.3 was taken as a NASICON-structured model system which is a candidate material for solid electrolytes in post-Li energy storage. The commercially available powder (NEI Coorp., USA) was consolidated using cold isostatic pressing before sintering. In order to compare NATP with the “classical” NASICON system, Na1+xZr2(SiO4)x(PO4)3−x (NaZSiP) was synthesized with compositions of x = 1.7 and x = 2, respectively, and characterized with regard to their ionic and thermal transport behavior. While ionic conductivity of the NaZSiP compositions was about more than two orders of magnitude higher than in NATP, the thermal conductivity of the NASICON compound showed an opposite behavior. The room temperature value was about a factor two higher in NATP compared to NaZSiP. While the thermal conductivity decreases with increasing temperature in NATP, it increases with increasing temperature in NaZSiP. However, the overall change of this thermal transport parameter over the measured temperature range from room temperature up to 800 °C appeared to be relatively small.