Luminescent properties of europium-activated yttrium gadolinium phosphates

Nanocrystalline Y 1 − x − y Gd x Eu y PO 4 phosphors have been prepared via precipitation from aqueous solutions. From their luminescence and excitation spectra, the intensity ratio I 615 / I 594 of the Eu 3+ luminescence bands corresponding to electric dipole and magnetic dipole transitions has been determined as a function of Gd 3+ content. The critical concentration and effective energy transfer radius in Y 1 − x − y Gd x Eu y PO 4 have been evaluated. Excitation of Gd 3+8 S J − 6 D J and 8 S J − 6 J J transitions to Eu 3+ luminescence excitation levels in Y 0.99 − x Gd x Eu 0.01 PO 4 involves efficient energy transfer. Under 250-nm excitation, the Eu 3+ luminescence yield in Y 0.99 − x Gd x Eu 0.01 PO 4 is a factor of 2.5–3 higher than that in Y 0.99 Eu 0.01 PO 4 .