The atomic H permeability, JH, of 10YSZ (fluorite-type) single crystals was measured (1800 to 1050K) by using the Nigara method. Two tubular specimens (diameter: 1.30 x 0.93cm; length: 3.35cm – specimen L) or length 1.00cm (specimen S), annealed (1570K, 6h) in air, were used to eliminate the permeation of supporting materials (Pt rings, alumina tube, alumina disk). Measurements were carried out after the specimen had been kept at 1800K for 20h. Here, JH was 3.97 x 10−7 to 2.79 x 10−9/mol/hcm when it was assumed that PH2 = 7.36 x 103Pa and PH2O = 2.30 x 103Pa outside of both specimens and that the Ar flow-rates to the inside of specimen L and specimen S were 21.5 and 16.9 to 19.9cm3/min, respectively. Log[JH] decreased with decreasing temperature, and was proportional to the reciprocal temperature. The activation energies were 0.61, 1.60 and 0.79eV at 1800 to 1680, 1680 to 1330 and 1330 to 1050K, respectively. The protonic conductivity, which was estimated from JH, and H partial pressures inside and outside of the specimens, was 2.4 x 10−6 to 1.5 x 10−8S/cm at 1800 to 1050K. The JH of other 10YSZ single crystal specimens, which were not annealed and which were measured after being kept at 1800K for 1h, was lower than that of the above specimens; especially at high temperatures. The activation energies were 1.27, 0.15 and 1.49eV at 1800 to 1425, 1425 to 1150 and 1150 to 1050K, respectively. The 10YSZ single crystal was an electron–proton mixed conductor under a H2–H2O atmosphere at high temperatures. Since the JH of 12YSZ single crystal specimens, which were annealed at 1870K for 24h in air and measured after being kept at 1800K for 18h, was less than 10−9/molhcm at 1800K, it was difficult to determine the relationship between H permeability and temperature.

Hydrogen Permeability of YSZ Single Crystals at High Temperatures. Y.Nigara, K.Yashiro, J.O.Hong, T.Kawada, J.Mizusaki: Solid State Ionics, 2004, 171[1-2], 61-7