Structure, optical properties and preferential site substitution of Eu3+ activated Ca8NaBi(PO4)6F2 red emitting phosphors prepared by modified Pechini process

Eu3+-doped and undoped Ca8NaBi(PO4)6F2:xEu (x = 0.01–0.5) apatite phosphors have been synthesized at 900 °C by the modified Pechini process. Their structural morphological characteristics were determined XRD, TEM Raman spectroscopy. The structure of host matrix was refined Rietveld method: Ca8NaBi(PO4)6F2 crystallizes in hexagonal class, sp. gr. P63/m, a b 9.3980 (6) Å, c 6.9039 (9) Å γ 120°). electronic simulated revealing an indirect bandgap 3.46 eV Eu3+ ions replace for Bi3+ ones two types sites: M1 (C3 symmetry IX-fold oxygen coordination) M2 (CS VII-fold coordination one fluoride six oxygens). doping induces redistribution over sites favor former species. transition probabilities using Judd-Ofelt theory yielding radiative lifetime 2.21 ms. It found that exhibit relatively weak luminescence quenching. CIE 1931 color coordinates compound with x 0.35 Eu are (0.648,0.352) falling red region corresponding to correlated temperature 2919 K purity >96%. thermal stability phosphor studied until 400 (the activation energy is 0.70 eV) indicating high temperatures. apatites promising as white-light LEDs.