Thermal Stability and Phase Transitions in WO3-ZrO2 and WO3-TiO2 Composites

Complex sol-gel process was applied to synthesize WO3-ZrO2 and WO3-TiO2 composites at different ratio of oxides. These composites are used to obtain radionuclide W-Re generators important due to applications in nuclear medicine. The structure of above composites depends on annealing temperature. At 800 °C specimens are fully crystalline containing separate oxides with crystallites of nanometric sizes. WO3 existing in monoclinic form stabilizes tetragonal ZrO2 form. Long time annealing at 1000 °C causes martensite type phase transition in ZrO2 from tetragonal to monoclinic form whereas in WO3-TiO2 composite in the same conditions phase transitions do not occur.