Aliovalent Ion Substitution and Enhanced Photoluminescence of Sr2SiO4:Tb3+/Z+ (Z = Li, Na, and K) Phosphors

The role of charge compensatory additives viz. monovalent ions (Li+, K+, and Na+) codoped with Tb3+ in strontium silicate phosphors is investigated. The addition of charge compensators enhances the luminescence intensity of the prepared phosphors because they neutralize the charge generated by Tb3+ substitution for Sr2+ ions. The vacancy and defects created due to Tb3+ ions are suitably minimized by the addition of aliovalent impurities in the host. As the Tb3+ concentration is increased, the green emission surpasses the blue emission due to cross relaxation following the energy transfer process. The role of monovalent Li+ ions among all charge compensator ions used was found to be most effective for enhanced Tb3+ ion emissions. As the Tb3+ concentration increases, the chromaticity coordinates shifts from the blue to green region and the correlated color temperature moves to the daylight region.