Effects of the fabrication process on the grain-boundary resistance in BaZr_0.9Y_0.1O_3−δ

This paper reports on the effect of the fabrication process on the conductivity of BZY10 (BaZr0.9Y0.1O3−δ). The dense specimens were prepared by four methods: (1) solid-state reactive sintering (SSRS), (2) conventional sintering using powder prepared by solid-state reaction and NiO as sintering aid, (3) conventional sintering using powder prepared by solid-state reaction followed by high-temperature annealing (HT), and (4) spark plasma sintering (SPS). The four specimens crystallize in a cubic structure, without any observable secondary phases. The AC conductivities of these four specimens were measured by impedance spectroscopy in moist reducing atmosphere from 600 to 200 °C; the grain boundary and bulk contributions were distinguished by the analysis of the low-temperature spectra. The grain-boundaries of the sample prepared by solid-state reactive sintering exhibited a resistance typical of the bulk material, while the three other specimens had more resistive grain boundaries. Similar activation energies for proton transport were obtained for the bulk resistance of the four specimens (0.39–0.42 eV). The activation energy for the grain boundaries increased from 0.45 eV for the solid-state reactive sintered BZY10 to 0.84 eV for the conventional solid-state reaction using NiO as sintering aid. This study highlights the potential of the solid-state reactive sintering process as a time and cost-effective method for producing dense ceramic with lower resistance BZY10 grain boundaries.