(Ca,Mg)9Gd1 –xEux(PO4)7 Red Phosphors Activated with Gd3+ and Eu3+

Abstract

Solid solutions with the whitlockite structure Ca₉Gd_{1 –х}Eu_x(PO₄)₇ and Ca₈MgGd_{1 –х}Eu_x(PO₄)₇ were synthesized by standart tecnique. The compounds have been characterized using various methods, including X-ray diffraction, second harmonic generation, and luminescence spectroscopy. The optical characteristics, excited-state lifetimes, and quantum yield were studieid. Under excitation at 395 nm, the compounds exhibit bright luminescence in the orange-red spectral region. The concentration of Eu³⁺ cation were optimized for obtaining the most efficient luminescence in the red spectral region: x = 0.75 for Ca₈MgGd_{1 –х}Eu_x(PO₄)₇ and x = 1 for Ca₉Gd_{1 –х}Eu_x(PO₄)₇. Efficient Gd³⁺ → Eu³⁺ energy transfer has been demonstrated, with an increase in photoluminescence intensity by a factor of 2.5. The quantum yield in the solid solutions reaches 49.5%, which is twice that in a commercially available Y₂O₃:Eu³⁺-based phosphor.