Effect of replacement of Ca by Ln (Ln = Y, Gd) on the structural and luminescence properties of CaWO4:Eu3+ red phosphors prepared via co-precipitation

Eu3+-doped calcium based tungstate, Ca1−xLnxWO4:Eu3+ (Ln = Y, Gd) red-emitting phosphors were prepared by co-precipitation method with NH4HCO3–NH3·H2O system as the precipitating aid agent. X-ray diffraction results reveal that the synthesized Ca1−xLnxWO4:Eu3+ have scheelite structure with pure phase. Infrared spectra show strong absorption peaks between 803 and 440 cm−1 which are assigned to the vibration of O–W in WO42− tetrahedron. The Energy Disperse Spectroscopy analysis reveals that the red phosphors have been successfully prepared by co-precipitation method according to theoretic ratio. Due to the 5D0–7F1–3 transitions of Eu3+ ions, photoluminescence spectra show a red emission at about 614 nm under excitation of 395 nm (commercial ultraviolet) and 465 nm (blue chip). With Ln lanthanide added in host, the luminescent intensity of Ca1−xLnxWO4:Eu3+ (x = 0.4, 0.5) is obviously improved comparing with that of CaWO4:Eu3+ by several times.