Aliovalent Ion Substitution and Enhanced Photoluminescence of Sr ₂ SiO ₄ :Tb ³⁺ /Z ⁺ (Z=Li, Na, and K) Phosphors

The role of charge compensatory additives viz. monovalent ions (Li ⁺ , K ⁺ , and Na ⁺ ) codoped with Tb ³⁺ 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 Tb ³⁺ substitution for Sr ²⁺ ions. The vacancy and defects created due to Tb ³⁺ ions are suitably minimized by the addition of aliovalent impurities in the host. As the Tb ³⁺ 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 Tb ³⁺ ion emissions. As the Tb ³⁺ concentration increases, the chromaticity coordinates shifts from the blue to green region and the correlated color temperature moves to the daylight region.