Luminescence in the system Al2O3-B2O3

Highlights: • Combustion synthesis of phosphors in Al₂O₃-B₂O₃ system reported. • Al₄B₂O₉, Al₅BO₉ and Al₁₈B₄O₃₃ were successfully prepared. • Luminescence of Ce³⁺ and Cr³⁺ observed in as-combusted powders. • Characteristic luminescence in form of narrow R lines of Cr³⁺ was observed in Al₅BO₉ and Al₁₈B₄O₃₃. -- Abstract: Three compounds in the system Al₂O₃-B₂O₃, viz. Al₄B₂O₉, Al₅BO₉ and Al₁₈B₄O₃₃ were successfully prepared by facile combustion synthesis. Activation by 3d transition element Cr³⁺ and 4f lanthanide Ce³⁺ was attempted. Characteristic luminescence in form of narrow R lines of Cr³⁺ was observed in Al₅BO₉ and Al₁₈B₄O₃₃. Interaction of Cr³⁺ with the surrounding was represented by the Racah parameters. Broad band emission of Ce³⁺ arising from allowed d-f transitions in near ultraviolet (nUV) region in all 3 compounds is reported for the first time.