Comparative study of thermal decomposition of the sol–gel products of U and Ce by external and internal gelation processes

Abstract The synthesis of U 0.7 Ce 0.3 O 2+ x was carried out using external gelation (with urea/NH 3 solution) and internal gelation (with urea/hexamethylene tetramine). The compounds formed were characterized using thermal analytical techniques in Ar, vacuum and air, X-ray powder diffraction and effluent gas analysis by mass spectrometry. The compound formed through external gelation was found to form UO 3 as an intermediate product (identified by O 2 loss to form U 3 O 8 ) whereas the compound formed through internal gelation resulted in single-phase UO 2 , which could be sintered into homogeneous pellets with 97% th.d. in Ar + 2% H 2 atmosphere at temperatures as low as 1100 °C.