Dual Color Emissions of Sr_2-xCa_xP₂O₇:Eu²⁺, Mn²⁺ for Near UV Excitation

Eu ²⁺, Mn ²⁺ singly and co-doped Sr _2-xCa _xP ₂O ₇ phosphors (x=0-2) are prepared by solid state reaction. Crystal phase evolution is studied as a function of Ca ²⁺ content based on the experimental measurements of X-ray diffraction, photoluminescence and fluorescence decay. The x dependent emission band shapes and peak positions for both Eu ²⁺ and Mn ²⁺ are discussed in terms of the crystal phase types and crystal eld strength in relation with Ca ²⁺ substitution for Sr ²⁺. An effective energy transfer from blue emitting Eu ²⁺ to orange emitting Mn ²⁺ is observed in all compositions beneficial to dual color emissions. The widest emission band and intense orange emission are found in Sr _1.25Ca _0.75P ₂O ₇: Eu ²⁺, Mn ²⁺, exhibiting promising use in white light generation using near UV LEDs.