Structural and optical properties of Sm3+-doped Ca2B2O5 phosphor: A promising orange-red emitting for n-UV solid state lighting

Sm 3+ -activated Ca 2 B 2 O 5 phosphor was prepared via a combustion route. Phase purity and single-phase monoclinic structure formation were confirmed by X-ray diffraction analysis, matching the standard PDF card No. 2008055. FE-SEM revealed agglomerated particles with irregular morphology. Elemental analysis by EDS shows the presence of Ca, B, and O elements. The photoluminescence study of Ca 2 B 2 O 5 :Sm 3+ phosphor observed three characteristic emission bands centered at 567 nm, 604 nm and 651 nm under near-UV excitation at 406 nm, corresponding to ⁴G₅ / ₂ → ⁶H₅ / ₂, ⁴G₅ / ₂ → ⁶H₇ / ₂, and ⁴G₅ / ₂ → ⁶H₉ / ₂ transitions. The maximum emission intensity was achieved at a dopant concentration of 0.5 mol%, further increase in concentration led to a decrease in intensity due to concentration quenching. Further, concentration quenching is explained using Blasse’s equation and Dexter’s theory. The Sm 3+ -activated Ca 2 B 2 O 5 phosphor critical transfer distance (R c ) was found to be 15.99 Å and decay time of τ = 2.5779 ms for the 0.5 mol%. The chromaticity coordinates of the dominant emission were found in the orange-red region, exhibiting a high color purity of about 94%. These results demonstrate that the Sm 3+ -activated Ca 2 B 2 O 5 phosphor is effective for near-UV-excited for solid state lighting.