Co-Doping Effect on the Optical Properties of Eu^(2+/3+) Doped in BaSiO₃

To investigate the effect of co-doping on the optical properties of Eu^(2+/3+) doped in Ba₀.₉₈SiO₃:0.02Eu, the series of Ba₀.₉₆SiO₃:0.02Eu, 0.02R^+/3+ (R⁺ = Li⁺, K⁺ or Na⁺, R³⁺ = La³⁺ or Y³⁺) phosphors were synthesized using a solid-state reaction method. The excitation efficiency due to the charge transfer band (CTB) was enhanced via co-doping of R⁺ and the emission intensity due to Eu³⁺ was thus increased by 3.7 times compared with that of the single-doped Ba₀.₉₈SiO₃:0.02Eu³⁺. However, the co-doping of R⁺ does not increase the emission intensity of Eu³⁺ via the direct ⁷F₀→⁵L₆ excitation of Eu³⁺, but rather decreases it. On the other hand, the emission intensities due to Eu²⁺ were decreased via the co-doping of R⁺ but increased via the co-doping of La³⁺. The present work reveals that the optical properties of Eu³⁺ or Eu²⁺ doped in BaSiO₃ depend not on the charge state (+ or 3+) of the co-doped ions, but on the co-doped element itself.