Origin of paramagnetic centres in GeO2–ZrO2 prepared by coprecipitation in aqueous solution

In the present work, we provide evidence of an unexpected increase in the paramagnetic centres (PC) concentration with increase in GeO2 (5–50 mol.%) content in GeO2–ZrO2 coprecipitates prepared by ammonia-promoted hydrolysis of ZrO(NO3)2 and GeO2 (hex) aqueous solutions followed by drying and gradual calcinations in air (300–900 °C). The possible mechanism of defects formation is proposed. An increase in PC concentration is associated with the peculiarities of Ge–Zr hydroxides thermal dehydration process and structure type transition.