A series of La2-xSrxCoO4.5-x/2 compounds, where x ranged from 0.5 to 1.5, was prepared as powder and ceramic shapes; using solid-state reactions. All of the compositions had a single-phase K2NiF4-type structure at 20 to 1000C in air. A reversible O desorption-sorption behaviour in Ar, during heating and cooling between 300 and 1050C, was observed. The amount of exchanged O was found to be a function of the x-value. At 0.5 to 0.8, the amount of exchanged O decreased to zero and, at 0.9 to 1.5, it increased to a maximum value. All of the O stoichiometry changes occurred within the range of the K2NiF4-type solid solution. The equilibrium values of electrical resistivity, for x = 1, were investigated as a function of temperature (400-1050C) and O partial pressure. Above 850C, the temperature coefficient of the conductivity of LaSrCoO4 became negative; with a maximum conductivity of 160S/cm.

Composition and Electrical Conductivity of Some Cobaltates of the Type, (La,Sr)2Co4.5. V.V.Vashook, H.Ullmann, O.P.Olshevskaya, V.P.Kulik, Y.E.Lukashevich, L.V.Kokhanovskij: Solid State Ionics, 2000, 138[1-2], 99-104