Red photoluminescence due to energy transfer from Eu²⁺ to Cr³⁺ in Sr₃Al₁₀SiO₂₀-SrAl ₁₂O₁₉ mixed phases

Sr₃Al₁₀SiO₂₀-SrAl₁₂O ₁₉, doped with Eu²⁺, Cr³⁺ and (Eu²⁺ + Cr³⁺) is prepared by solid-state reaction and energy transfer from Eu²⁺ to Cr³⁺ in the phase of Sr₃Al ₁₀SiO₂₀ is the focus of investigation. The spectrum of Sr₃Al₁₀SiO₂₀-SrAl₁₂O₁₉ : Eu²⁺ shows f-d emission bands at 460 and 400 nm. Cr³⁺ doped Sr₃Al₁₀SiO₂₀-SrAl₁₂O ₁₉ yields emission lines at 688 and 696 nm and a broad emission band between 650 and 750 nm. The photoluminescence study and fluorescence lifetime measurements demonstrate efficient energy transfer from Eu²⁺ to Cr³⁺ in Sr₃Al₁₀SiO₂₀ : Eu ²⁺, Cr³⁺. The emission lines peak at 688 nm and 696 nm, which, respectively, originate from ²E-⁴A₂ transitions in the phases of SrAl₁₂O₁₉ and Sr ₃Al₁₀SiO₂₀. The broad emission band of Cr ³⁺ between 650 and 750 nm in the phase of Sr₃Al ₁₀SiO₂₀ is considered to be the ⁴T ₂-⁴A₂ transition by calculating the strength of the octahedral crystal field Dq, the Racah parameters B and C as well as by constructing the Tanabe-Sugano diagram.