Evolution of the EFG during the beta to cubic phase transition in ScSZ

M.A. TAYLOR,M. C. CARACOCHE,M. KILO, G. BORCHARDT

La Plata, Argentina

Workshop; International Workshop 35th Anniversary of Hyperfine Interactions at La Plata; 2005

Cubic stabilized zirconia is widely used as a solid electrolyte in solid oxide fuel cells and oxygen sensors because of its high ionic conductivity at elevated temperatures. Zirconia can be stabilized in its cubic form by doping it with lower valent oxides, e.g. CaO, Y2O3, or Sc2O3 (leading to CSZ, YSZ, or ScSZ ceramics). Among these systems, scandia-doped zirconia exhibits the highest conductivity known. However, the Sc2O3–ZrO2 phase diagram is more complex than those of other pseudo-binary M2O3–ZrO2 systems and the presence of rhombohedral phases is reported in the concentration range where the highest oxygen conductivity is observed (10–12 mol% Sc2O3). The low-conductivity rhombohedral b-phase is stable at temperatures below 500 and 600°C [1,2]. ScSZ single crystals were prepared by skull-melting [3] starting from Sc2O3 and ZrO2 powders of >99.99% purity by Prof. Assmus at the University of Frankfurt radio frequency 3.7 MHz, input power 16.5 kW). XRD experiments performed in powders obtained after milling the crystals (Co, wavelength = 1.789007 Å, time per position = 5s, step = 0.02º,) indicate that the major phase is the b- rhombohedral one, with less than 5% of cubic phase. In order to understand the local thermal changes produced across the phase transition, PAC experiments using two CsF-detector set-up (2t=0.75ns) supplied with an electric furnace which permitted heating the sample in-situ were performed. The 181Hf activity was implanted in the samples at the ISKP- Uni-Bonn.