The origin of defects formation in nanosized zirconia

In the present work, we provide evidence of an increase in the Zr3+ paramagnetic center concentration under colloidal transformation in ZrO2 prepared by the totally inorganic sol-gel method. The samples of thermally treated (100-950 °C in air) ZrO2 precipitates and dried sol-gel products-xerogels-were examined by TEM, XRD, DTA, EPR and IR-spectroscopy. Under the same heat treatment condition, the concentration of Zr3+ (axially symmetric signal at g⊥ = 1.977-1.979 and g‖ = 1.958-1.963) became higher in the xerogel samples rather than in precipitate samples and reached the maximum (∼ 1018 g− 1 in xerogel) after calcinations at 500 °C in air.