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

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 angstrom because of eight neighbors for 1100 degrees C heated undoped ZrO2, and the Zr-Zr bond lengths are 3.481 and 3.642 angstrom because of four and eight neighbors for 1100 degrees 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 angstrom and 2.45 angstrom in coated sample, whereas there is one shell with bond length of 2.32 angstrom for doped sample prepared at 1100 degrees 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.