Nanograin size of about 3-5nm of 20mol% Y-doped BaZrO3 (BZY20) proton conducting solid electrolyte was prepared at low processing temperature (< 200C) and a bulk nanograined sample was obtained at room temperature using cubic anvil pressing at 4GPa. The grain morphology and structural changes of the as-pressed and annealed BZY20 samples were studied using powder X-ray diffraction, high-resolution transmission electron microscope equipped with energy dispersive X-ray and electron diffraction analyses. Due to the presence of inhomogeneity such as trace formations of hydroxide phases of the as-pressed sample as observed from thermogravimetric and differential thermal analysis (TG/DTA), Fourier transform infra-red results, and from the thermodynamics phase equilibria viewpoint, the conductivity was immeasurable. On the other hand, the sample annealed at 800C with about 10nm grain size shows a rather low protonic conductivity possibly due to poor interfacial grain boundary contacts and structurally disordered interface. However, as the grain grows to a well-crystallized structure with better interfacial and refined grain boundary and better yttrium distribution from grain interior to the grain boundaries, the total protonic conductivity increased and shows a good agreement with the results obtained using proton and deuteron isotope exchange reaction. The total protonic conductivities, bulk and grain boundary contributions, at 500C for samples annealed at 800, 1250 and 1500C were 8.7 x 10−6, 2 x 10−3 and 4 x 10−3S/cm with grain sizes of about 10, 50 and 200nm, respectively.

Structural Study and Proton Transport of Bulk Nanograined Y-Doped BaZrO3 Oxide Protonics Materials. R.B.Cervera, Y.Oyama, S.Miyoshi, K.Kobayashi, T.Yagi, S.Yamaguchi: Solid State Ionics, 2008, 179[7-8], 236-42