Luminescence investigation and thermal stability study of Eu ²⁺ and Eu ²⁺-Mn ²⁺ codoped (Ba,Sr)Mg ₂Al ₆Si ₉O ₃₀ phosphor

Eu ²⁺ and Eu ²⁺-Mn ²⁺ codoped (Ba,Sr)Mg ₂Al ₆Si ₉O ₃₀ phosphors have been synthesized by solid state reaction, and their luminescent properties are investigated. Under the excitation of 330 nm, it is observed that the emission of Eu ²⁺ consists of two emission bands, located at around 370 and 450 nm, which are attributed to two Eu ²⁺ centers (Eu ²⁺(I) and Eu ²⁺(II)) ions substituting for two different Ba ²⁺ and Mg ²⁺ sites, respectively. As Sr ²⁺ gradually substitutes Ba ²⁺, the emission bands of Eu ²⁺(I) shift to longer wavelength whereas the emission bands of Eu ²⁺(II) exhibit no change. This phenomenon is discussed in terms of the crystal-field strength. A detail analysis on the energy transfer from Eu ²⁺ to Mn ²⁺ in SrMg ₂Al ₆Si ₉O ₃₀ host is presented, which indicates the energy of the red emission of Mn ²⁺ is derived mainly from Eu ²⁺(I). We have also demonstrated that BaMg ₂Al ₆Si ₉O ₃₀:Eu ²⁺, Mn ²⁺ exhibits better thermal quenching properties than that of SrMg ₂Al ₆Si ₉O ₃₀:Eu ²⁺, Mn ²⁺ because of bigger activation energy.