The reaction products from CeO2 and WO3 were studied by quenching method and TG–DTA in air, oxygen and argon (PO2=10–5 atm) atmospheres at 650~1400°C. Two new binary oxides, 2 Ce2O3•9 WO3 and Ce2O3•2 WO3, were found in addition to well–known Ce2O3•3 WO3. Their X–ray powder diffraction patterns, chemical and magnetic properties, and melting points and transition points were studied. The mp were 1026±10°C for 2Ce2O3•9 WO3, 1070±10°C for Ce2O3•3 WO3, and 1395 ± 10°C for Ce2O3•2 WO3. CeaO3•3 WO3 and Ce2O3•2 WO3 had the reversible transition point at 1005 ± 10°C and 1105 ± 10°C, respectively. Different products were obtained according to atmospheres and temperatures, even if same reactants were used. That is, Ce2O3•2 WO3 was not stable and decomposed to Ce2O3•3 WO3 and CeO2 in air and oxygen, or in argon below 790°C, and Ce2O3•3 WO3 was also unstable and decomposed to 2 Ce2O3•9 WO3 and CeO2 in air below 830°C, or in oxygen below 890°C. These results show that the preparation and decompositison of these compounds can be represented by the following equilibrium reactions, 4 CeO2 + 9 WO8 = 2 Ce2O3•9 WO3 + O2 (1) 4 CeO2 + 2(2 Ce2O8•9 WO3) = 6(Ce2O3•3 WO3) + O2 (2) 4 CeO2 + 4(Ce2O3•3 WO3) = 6(CeaO3•2 WO3) + O2 (3) The phase relation for these equations in the equilibrium oxgen pressures was determined. The stable region of each compound was shown in PO2–T diagram.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)