Thermoanalysis of the system BaO2BaOO2

Structural Properties of Nonstoichiometric Barium and Strontium Peroxides: BaO2−x (1.97≥2−x≥1.72) and SrO2−x (1.98≥2−x≥1.90)

“…1. Although Bernal's structural model is essentially correct, some re"nement is needed: thermoanalytical measurements (2,3) suggest that barium peroxide is a nonstoichiometric compound, as is supported by the recent single crystal X-ray Present address: Davy Faraday Research Laboratory, The Royal Institution of Great Britain, 21 Albermarle Street, London W1X 4BS, U.K. structure determinations on the compound by VerNooy (4) and on strontium peroxide by Range et al (5), although due to the high standard deviations of the compositions of the peroxide crystals in the two studies this "nding cannot be con"rmed with certainty. Furthermore, in neither of these studies was it possible to prove the presence of oxide ions in the crystal lattice, as is required for nonstoichiometric compounds.…”

Thermodynamic Modeling of the Binary Barium–Oxygen System

“…and Mayorova et al 27 . Additionally, the evidence offered by Aptekar et al ., 16,17 Emelchenko et al ., 26 and Mayorova et al 27 . against the presence of the liquid phase at 1071K is more compelling since these experiments were done over a wide range of pressures, as opposed to the 1 atm experiments by Hedvall 24 and Kedrovskii et al 25 .…”

“…established the pressure‐temperature ( P‐T ) relationship for the BaO, BaO 2 , and gas three‐phase equilibrium for temperatures up to 1345 K. Since the experimental ln P versus 1/ T relationship did not change its slope over the studied pressure and temperature ranges, the authors 16,17 concluded that this relationship represented the same BaO, BaO 2 , and gas three‐phase equilibrium and that the liquid phase did not participate in any invariant reactions with BaO and gas at least up to 1345 K and 20 atm. Mayorova et al 27 . studied the gas, BaO and BaO 2 three‐phase equilibrium up to 1.5 atm and 1112 K and did not observe the presence of the liquid phase either.…”

“…were performed with less pure starting materials than those used by Aptekar et al 16,17 . and Mayorova et al 27 . Additionally, the evidence offered by Aptekar et al ., 16,17 Emelchenko et al ., 26 and Mayorova et al 27 .…”

“… The calculated phase diagram of the binary Ba–O system at 1atm using the parameters in Table II with the two‐phase model for the BaO and BaO 2 phases in comparison with the experimental data ▾, 18 ▪, 19 ▴, 20 • 21 for melting point of the BaO phase; ▵, 22 ▿ 23 for the liquidus; □, 17 ○, 25 * 27 for the BaO, BaO 2 and gas three‐phase equilibrium. Dotted‐lines are calculated using the parameters by Zimmermann et al 7 …”