Synthesis of zirconium and hafnium germanates from mechanically activated oxides

The peculiarities of the synthesis of zirconium and hafnium germanates (ZrGeO4 and HfGeO4) from mechanically activated oxides (GeO2, ZrO2 and HfO2) have been studied. The phase, structural and morphological evolutions of the products obtained by thermal treatment of mechanically activated oxides were studied by a set of analytical techniques. The results showed a significant decrease in GeO2 crystallite size during mechanical treatment, whereas the size of HfO2 and ZrO2 changes only slightly. Mechanical treatment of mixtures results in great change of morphology, an increase in particles contact area and partial amorphization of GeO2. Mechanical activation promotes a significant reduction of the temperature of compound formation, reaction rate and yield. Possible mechanisms of activation effect are discussed.