Structural evolution induced by substitution of designated molybdate sites (MoO4−2) with different anionic groups (BO3−3, PO4−3 and SO4−2) in CaMoO4:Sm3+ phosphors-A study on color tunable luminescent properties

A series of novel red emitting CaMoO4:Sm3+ (1.0 mol %) phosphors substituted with different anionic groups (BO3−3, PO4−3 and SO4−2) were prepared using a high temperature solid state reaction method. The effects of anionic substitution on the crystalline structure and photoluminescence (PL) properties of the CaMoO4:Sm3+, CaMoO4-BO3:Sm3+, CaMoO4-PO4:Sm3+and CaMoO4-SO4:Sm3+ phosphors were investigated. The structure, particle morphology, chemical composition, vibration modes, and PL properties of the phosphors were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectrometry (FT-IR) and PL spectroscopy, respectively. The XRD patterns indicated that the crystalline structures of all the samples were consistent with the standard scheelite structure of CaMoO4. The structural parameters of the pure phase of CaMoO4:Sm3+ phosphor were obtained from the Rietveld analysis. Red PL attributed to the 4G5/2 → 6H9/2 transition of Sm3+ was observed at 646 nm when the CaMoO4:Sm3+ samples were excited by 404 nm using a monochromatized Xenon lamp. Furthermore, orange-red color tunable emission has been achieved by substitution of different anionic groups (BO3−3, PO4−3 and SO4−2) into the CaMoO4:Sm3+ phosphors. Among all the studied phosphors, the CaMoO4-SO4:Sm3+ phosphor showed the strongest PL emission compared to all other phosphors suggesting that it is a promising potential candidate for red emission in the near UV excited white LED applications.