OXYGEN NONSTOICHIOMETRY AND ELECTRICAL-CONDUCTIVITY OF THE SOLID-SOLUTIONS LA2-XSRXNIOY LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.5)

Oxygen nonstoichiometry and electrical resistance of a series La2-xSrx NiOy solid solutions, where x = 0.0, 0.2 and 0.5 in argon flows at oxy gen partial pressures 1.5, 10.2, 49.2, 100 and 286 Pa within the tempe rature range of 20-1050 degrees C were studied. Nickelate oxygen desor ption/sorption spectra when heating-cooling at constant rate demonstra ted strong dependence of cation composition of the samples. Unlike La1 .5Sr0.5NiOy compounds those of La2NiOy and La1.8Sr0.2NiOy have weakly bonded oxygen, capable to exchange reversibly with the gas phase at th e temperatures higher than 250 degrees C. The equilibrium values of ox ygen nonstoichiometry and specific resistance for the these nickelates were determined at 300-1050 degrees C and p(O2) = 1.5-286 Pa as a fun ctions of temperature versus oxygen partial pressure. All nickelate st udied appear to be p-type conductors with metal electric conductivity at equilibrium states. (C) 1998 Elsevier Science B.V. All rights reser ved.