Study of Structure of Defect Centers in Europium Vanadate Nanoparticles with Heterovalent Dopants

The EuVO4 nanoparticles doped with Ca²⁺ impurities were synthesized by citrate-nitrate sol-gel method and investigated. Diffuse reflection spectra of the EuVO4:Ca samples contain two additional bands around 400 and 470 nm those were not observed for the undoped EuVO4. These bands were ascribed to Ca-induced defects in the vanadate crystal lattice. Origin of these defects is studied taking into account results of high resolution XRD measurements. The additive XRD peaks were found for the Eu0.8Ca0.2VO4, sample. These peaks were identified as traces of the Ca2V2O7 second crystal phase in the synthesized nanoparticles. The maximal concentrations of the Ca²⁺ heterovalent impurity permits to keep single phase EuVO4:Ca sol-gel nanoparticles were estimated.