The role of compensation defects in Eu3+ stabilization under reductive atmosphere in Sr2SiO4 matrix

Luminescent materials based on strontium orthosilicate doped with a fixed concentration of europium and co-doped with various concentrations of sodium, lithium and boron were synthesized in order to study the role of co-dopants in luminescent properties of europium ions. The obtained materials were characterized using powder X-ray diffraction (XRD) technique. The results of the optical measurements indicate that the incorporation of sodium or lithium increases emission intensity of Eu3+, but does not stabilize Eu3+ under reductive (5% H2/N2) atmosphere, which was observed for the boron co-doping. Moreover, it is shown that the sodium or lithium co-doping facilitates the reduction process of Eu3+ → Eu2+. The obtained results suggest that diffusion limited processes are crucial for the stabilization of Eu3+ during the reduction step of synthesis.