Energetics of la_2-xsr_xcoo_4-y (0.5 < x < 1.5)

Several compositions in the La_2-xSr_xCoO_4-y series were synthesized in air and in argon. The heats of formation of these compounds were calculated from the measured heats of solution using high-temperature drop solution calorimetry in lead borate solvent. The heats of formation become more exothermic with increasing strontium content, consistent with a high heat of oxidation of -400 kJ per mole of O₂ determined from calorimetry of samples with the same strontium content and different oxygen nonstoichiometry. This enthalpy of oxidation is significantly more exothermic than values for the corresponding cuprates and nickelates.