Role of the Sintering Temperature and Doping Level in the Structural and Spectral Properties of Eu-Doped Nanocrystalline YVO4

A sol-gel approach was employed to prepare nanosized YVO4 nanopowders doped with Eu3+ ions. Raw nanomaterials were thermally treated at 700-1000 degrees C for 3 h. X-ray diffraction (XD) analysis demonstrated that single-phase nanopowders with high crystallite dispersion were obtained. Our studies were focused on relating the luminescence properties of the Eu3+ dopant to the nanocrystallite (NC) size. Depending on the thermal treatment, the average NC size was calculated to range from 20 nm to 1.1 mu m. We have found that the size effect manifests mainly in the expansion of the cell volume and broadening of XRD peaks, as indicated by Rietveld analysis. Moreover, emission and excitation spectra, although typical for the Eu3+ ions, demonstrated some degree of correlation with the calcination temperature and doping concentration. To explain these differences a detailed analysis of the luminescence spectra by the Judd-Ofelt theory has been performed.