Elaboration of blue-emitting blue pigments based on Eu²⁺/Co ²⁺ codoped BaMgAl₁₀O₁₇ through the heterogeneous distribution of dopants

Photoluminescence and coloring properties of Eu²⁺/Co ²⁺ codoped BaMgAl₁₀O₁₇ were investigated to produce inorganic blue-luminescent pigments. Two kinds of synthesis methods were employed for BaMgAl₁₀O₁₇:Eu²⁺,Co²⁺ powders based on a conventional solid-state reaction and a newly developed precipitation method. Powder samples through the solid-state reaction exhibited blue photoluminescence from Eu²⁺, which was quenched considerably by codoping with Co²⁺ due to the occurrence of a Eu²⁺ → Co²⁺ energy transfer. The precipitation method was then conceived to separate Eu²⁺ and Co²⁺ spatially in a BaMgAl ₁₀O₁₇ particle. Powder samples through the precipitation method could be colored blue by optical absorption of Co²⁺ without degrading blue photoluminescence from Eu²⁺. The inhomogeneous distribution of the Eu²⁺/Co²⁺ dopants in the BaMgAl ₁₀O₁₇ particles was instrumental to the suppression of the Eu²⁺ → Co²⁺ energy transfer.