THERMOANALYSIS OF THE SYSTEM BAO2-BAO-O2

Thermoanalysis of the system BaO2-BaO-O2 has been carried out at oxyge n pressures from 0.2 to 1.5 atmospheres using a Netzsch STA-409 simult aneous analyser. Measurements were made over the temperature range fro m 25 to 950-degrees-C. The thermogravimetric data obtained have been u sed to evaluate the non-stoichometric region boundaries for BaO2 and t o estimate the same region for BaO. The temperatures of the monovarian t equilibrium BaO1+x1-BaO2-x2 have been determined: T(mon) = 990, 1041 , 1083 and 1109 K at P(O2) = 0.2, 0.5, 1.0 and 1.5 oxygen atmospheres, respectively. For the reaction BaO1.0 + 0.5O2 = BaO2.0, the values DE LTAG(T)theta = -5.1, -2.1, 0.3, and 1.7 kJ mol-1 have been calculated for the above respective temperatures.