Effect of co-doping of alkali metal ions on CaRE(MoO):Eu (RE = Y, La) phosphors with enhanced luminescence properties

A series of Ca 0.5 RE 1 x (MoO 4 ) 2 : x Eu 3+ ,M + (RE = Y, La; M = Li, K and Na) phosphors were synthesized by a facile hydrothermal method. X-ray diffraction suggested that these phosphors could be indexed to a scheelite tetragonal Ca 0.5 RE 1 x (MoO 4 ) 2 (RE = Y, La) phase with a space group of I 4 1 / a with high purity. FESEM indicated the signs of bi-pyramid-like micro-architectures. Elemental mapping analysis provided evidence of the incorporation and uniform distribution of all the elements. X-ray photoelectron spectroscopy (XPS) confirmed the presence of all the elements. The PL properties of Ca 0.5 RE 1 x (MoO 4 ) 2 : x Eu 3+ ,M + (RE = Y, La; M = Li, K and Na) phosphors were analysed extensively. The obtained results suggest that the characteristic red emission is due to the hypersensitive electric dipole 5 D 0 7 F 2 transition. The emission intensity of Ca 0.5 RE 1 x (MoO 4 ) 2 : x Eu 3+ ,Na + (RE = Y, La) is higher than Li + and K + co-doped Ca 0.5 RE 1 x (MoO 4 ) 2 : x Eu 3+ (RE = Y, La). This can be explained by the charge compensation effect. JuddOfelt theory was adopted to examine the photophysical properties. The luminescence decay time values were estimated. The CIE chromaticity co-ordinates were derived from the emission spectra and the values were found to be close to the NTSC standard values. Hence, the prepared phosphors are suitable for display applications. Illustration of elemental mapping and PL emission spectra of the phosphors, Ca 0.5 RE 1 x (MoO 4 ) 2 :Eu 3+ ,M + (RE = Y, La; M = Li, K and Na).