Solvothermal Synthesis, Structural Characterization and Optical Properties of Pr-Doped CeO[sub.2] and Their Degradation for Acid Orange 7

Pr-doped CeO[sub.2] with different doping levels was prepared from Ce(NO[sub.3])[sub.3]∙6H[sub.2]O and Pr(NO[sub.3])[sub.3]∙6H[sub.2]O by solvothermal method without any additional reagents, in which the mixed solution of ethylene glycol and distilled water was employed as a solvent. The influences of Pr-doping on phase composition, crystal structure and morphology were investigated, as well as Pr valence and oxygen vacancy defects. The Pr cations entered into the CeO[sub.2] crystal lattice with normal trivalence and formed a Pr-CeO[sub.2] solid solution based on the fluorite structure. The larger trivalent Pr was substituted for tetravalent Ce in the CeO[sub.2] crystal and compensated by oxygen vacancy defects, which caused the local lattice expansion of the crystal lattice. Moreover, the Pr-doped CeO[sub.2] solid solutions exhibited visible color variation from bright cream via brick red to dark brown with the increasing of Pr contents. The degradation of AO7 dye was also investigated using a domestic medical ultraviolet lamp; the removal efficiency of AO7 by 1% and 2% Pr-doped CeO[sub.2] approached 100%, much higher than 66.2% for undoped CeO[sub.2].