Enhanced luminescence by monovalent alkali metal ions in Sr₂SiO₄:Eu³⁺ nanophosphor prepared by low temperature solution combustion method

Graphical abstract: PL spectra of Sr₂SiO₄:Eu³⁺ nanophosphor co-doped with Li⁺, Na⁺ and K⁺ metal ions. - Highlights: • Sr₂SiO₄:Eu³⁺:M⁺ (Na⁺, K⁺ and Li⁺) were prepared by simple low temperature combustion method. • XRD, SEM, TEM and UV–Vis techniques used to characterize the phosphor. • TL and PL properties were well studied. • Prepared phosphor may be used for making the white LED and dosimetric applications. • The color purity has been verified by using the chromaticity diagram. - Abstract: A series of red light emission phosphors of Sr₂SiO₄:Eu³⁺ (1–5 mol%) and Sr₂SiO₄:Eu³⁺:M⁺ (M⁺ = Na⁺, K⁺ and Li⁺) were prepared through simple low temperature solution combustion method and their luminescence properties were studied. The powder X-ray diffraction (XRD) results revealed the formation of highly crystalline Sr₂SiO₄:Eu³⁺ nanophosphor having an average particle size 45–60 nm and strain was measured to be (2.4–3.1) × 10³. The SEM pictures of Sr₂SiO₄:Eu³⁺ and Sr₂SiO₄:Eu³⁺: M⁺ showed porous in nature and irregular shaped particles. The phosphors can be effectively excited by the light of 395 nm and show the characteristic emission peaks assigned to transitions of ⁵D₀ → ⁴F_J (J = 0, 1, 2, 3, 4). The excitation and emission spectra indicate that the phosphors can be effectively excited by UV (∼395 nm) light which emits an intense red light peaked at ∼614 nm. The Eu³⁺ concentration quenching mechanism was verified to be multipole–multipole interaction and critical energy transfer distance (R_C) was 16.43 nm. The effects of different concentration of Eu³⁺ and charge compensations on luminescence properties were discussed. The highest PL intensity was recorded for 4 mol% Eu³⁺ ions. Further, Li⁺ (0.03) has the best charge compensation effect followed by Na⁺ and K⁺ respectively. The γ-induced studies showed three glow peaks at 211, 163 and 243 (shouldered peaks) respectively at a warming rate of 5 °C s⁻¹. The glow peak intensity at 163 °C increases linearly up to 3 kGy and after that it decreases. Up to 3 kGy, the phosphor was quite useful for radiation dosimetry