ChemInform Abstract: Enhanced Low‐Temperature Proton Conduction in Sr_0.02La_0.98NbO_4‐δ by Scheelite Phase Retention.

Abstract

0.02 La 0.98 NbO 4-δ by Scheelite Phase Retention. -Powders of Sr0.02La0.98Nb1-xVxO4-δ (x = 0.15-0.5) are prepared by solid state synthesis of stoichiometric mixtures of SrCO3, La2O3, Nb2O5, and V2O5 (1300°C, 10 h). Sr0.02La0.98Nb0.7V0.3O4-δ maintains a constant thermal expansion coefficient up to 1000°C. The compound exhibits pure proton conduction of higher conductivity than the parent compound Sr 0.02 La 0.98 NbO 4-δ in the low-temperature range under wet oxidizing conditions. -(BRANDAO, A. D.; ANTUNES, I.; FRADE, J. R.; TORRE, J.; KHARTON, V. V.; FAGG*, D. P.; Chem. Mater. 22 (2010) 24, 6673-6683, http://dx.doi.org/10.1021/cm102705e ; Nanotechnol. Res. Div., Univ. Aveiro, P-3810 Aveiro, Port.; Eng.) -W. Pewestorf 10-010

Enhanced electrical conductivity of Mo-doped LaNbO4

“…11 Ca and Ta co-doping increases the transformation temperature to near 800 • C 12 ; and Sr and V codoping pushes the transformation temperature down to below room temperature. 13 In the present study, Mo-doped LaNbO 4 was investigated, aiming to improve the conductivity and stabilize the tetragonal phase. * Corresponding author.…”

Antimony substituted lanthanum orthoniobate proton conductor – Structure and electronic properties

“…The main strategy for shifting the phase transition temperature is the substitution of niobium by other penta‐ or tri‐valent elements like antimony, 5‐8 vanadium, 8‐10 arsenic, 11 or tantalum 8,12‐14 . Differences in ionic radius and electronegativity compared to niobium result in either elevating (for Ta) or decreasing (for Sb, V, and As) the transition temperature 11 …”

“…Therefore the phase transition occurs with a change in niobium coordination number (from 6 to 4) and no change in coordination of lanthanum. 4 The main strategy for shifting the phase transition temperature is the substitution of niobium by other penta-or tri-valent elements like antimony, [5][6][7][8] vanadium, [8][9][10] arsenic, 11 or tantalum. 8,[12][13][14] Differences in ionic radius and electronegativity compared to niobium result in either elevating (for Ta) or decreasing (for Sb, V, and As) the transition temperature.…”

Spark Plasma Sintering and Hot Pressing of Hetero‐Doped LaNbO4

“…In the case of La30, the conductivity was lowered due to bulk La 3 NbO 7 percolation, as the conductivity of this phase is lower than for the Ca‐doped LaNbO 4 . Finally, recent attempts of homo‐doping of LaNbO 4 have not been particularly successful with respect to increasing the proton conductivity . It seems therefore difficult to increase the proton conductivity of LaNbO 4 above the level reported initially …”