Strong Eu3+ luminescence in Lа1-x-yErx/2Eux/2CayVO4 nanocrystals: The result of co-doping optimization

Co-doped with Ca2+ and Er3+ ions LаVO4:Eu crystalline nanoparticles are synthesized and investigated with a goal to clarify the mechanisms of Ca2+ and Er3+ impurities effects on Eu3+ ions luminescence and to find compositions with enhanced luminescence intensity. The XRD analysis reveals dependence of crystal structure on dopants concentration: monoclinic crystal phase is observed for low dopant concentrations and content of tetragonal crystal phase increases with dopant concentrations increase. The SEM investigation reveals formation of nanoparticles with two types of shapes. Photoluminescence spectra consist of lines caused by f-f transitions in the Er3+ and Eu3+ ions. It has been shown that dependence of the Eu3+ ions luminescence intensity on the Er3+ and Ca2+ concentrations is caused by cumulative effects of dopants on crystal lattice structure, on defects in the first coordination sphere of the Eu3+ ions and on efficiency of excitation energy transfer. The maximal luminescence intensity is found for the Lа0.8Er0.05Eu0.05Ca0·1VO4 composition. The corresponded intensity is as much as 19 ± 2 and 8 ± 2 times higher than luminescence intensity of the Lа0.95Eu0.05VO4 and Lа0.9Eu0.05Ca0·05VO4 compounds, respectively. Conclusion is made that Er3+ and Ca2+ ions co-doping is a promising way to increase luminescence efficiency of the Eu3+ ions in the LaVO4 nanocrystals.