Thermal Stability and Phase Transitions in WO_3-ZrO_2 and WO_3-TiO_2 Composites

摘要

Complex sol-gel process was applied to synthesize WO_3-ZrO_2 and WO_3-TiO_2 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℃ specimens are fully crystalline containing separate oxides with crystallites of nanometric sizes. WO_3 existing in monoclinic form stabilizes tetragonal ZrO_2 form. Long time annealing at 1000℃ causes martensite type phase transition in ZrO_2 from tetragonal to monoclinic form whereas in WO_3-TiO_2 composite in the same conditions phase transitions do not occur.