Understanding the local structures of Eu and Zr in Eu₂O₃ doped and coated ZrO₂ nanocrystals by EXAFS study

Abstract

The role of surface coating, doping, and heating on the modification of crystal structure of ZrO₂, on the local structure of Zr and Eu, and on the photoluminescence properties of Eu₂O₃ doped and coated ZrO₂ nanocrystals has been studied. X-ray absorption fine structure measurements were carried out to understand the local environment surrounding Zr and Eu ions in Eu-doped and coated ZrO₂ nanocrystals. It is found that the local structure of Zr ion has been modified by changing the crystal phase and surface coating. The Zr−Zr bond length is 3.447 Å because of eight neighbors for 1100 °C heated undoped ZrO₂, and the Zr−Zr bond lengths are 3.481 and 3.642 Å because of four and eight neighbors for 1100 °C heated Eu-doped ZrO₂ sample. The oxygen ions around the central Eu ion are distributed in two shells with bond lengths of 2.26 Å and 2.45 Å in coated sample, whereas there is one shell with bond length of 2.32 Å for doped sample prepared at 1100 °C. Analysis suggests that the interatomic distance between Eu and neighboring atoms, the coordination number, and the bond length of doped nanocrystals are different from the coated nanocrystals. It is observed that local structures play the most important role on the modifications of luminescence properties observed in Eu-doped and coated ZrO₂ nanocrystals.