Composition and conductivity of some nickelates

Oxygen nonstoichiometry and electrical resistance of a series of La2-xSrxNi O4+/-delta solid solutions with x = 0.0-1.4 were investigated in argon/O-2 (p(O2) = 1.5-286 Pa) within a temperature range of 20-1050 degrees C. The o xygen permeability of gas tight ceramics was determined. Increasing stronti um content from 0 to 0.4 was found to decrease the amount of weak bonded ox ygen, which can be reversibly exchanged with oxygen in the gaseous phase (T = 250-550 degrees C). The equilibrium values of oxygen nonstoichiometry an d specific resistance of the nickelates with 0.0 less than or equal to x le ss than or equal to 0.5 were determined as functions of temperature and oxy gen partial pressure. The nickelates studied appear to be p-type conductors . Oxygen permeability of nickelates with x = 0-0.4 increases in accordance with the increasing range of the oxygen nonstoichiometry (T > 800 degrees C , the p(O2) gradient is (0.21 x 10(5) to 200) Pa). (C) 1999 Elsevier Scienc e B.V. All rights reserved.