The up-converting ZrO₂:Yb³⁺,E³⁺ nanomaterials were prepared with the combustion and sal-gel methods. The structure of the materials was cubic except for the minor monoclinic and tetragonal impurities associated with the use of the sal-gel method. The XANES results revealed only the trivalent form for both the Yb and Er dopants. The distance distributions calculated from EXAFS confirm that Er³⁺ and Yb³⁺ occupy the Zr-IV site in the structure. The nanomaterials show red (650-700 nm) and very weak green (520-560 nm) up-conversion luminescence due to the ⁴F_9/2 → ⁴I_15/2 and (²H_11/2,⁴S_3/2) → ⁴I_15/2 transitions of Er³⁺, respectively. The nanomaterials obtained with the combustion synthesis yield the most intense luminescence though showing significant afterglow, as well. The thermoluminescence measurements revealed the existence of traps with depths between 0.68 and 1.03 eV well matching to room temperature persistent emission. Finally, the mechanism for the persistent up-conversion luminescence was introduced based on the experimental results and discussed. (C) 2014 Elsevier B.V. All rights reserved.