Synthesis, phase transition and photoluminescence studies on Eu3+-substituted double perovskites—A novel orange-red phosphor for solid-state lighting

Photoluminescence studies on Eu3+-doped double perovskites with the formula A2CaWO6 (A=Sr, Ba) revealed that the forced electric dipole (ED) transition is present when Eu3+ is substituted at the non-centrosymmetric Sr-site vis-a-vis substitution at the centrosymmetric Ca-site shows both ED and magnetic dipole (MD) transition. A series of novel orange-red-emitting phosphor compositions Sr1.9−xBaxEu0.05Li0.05CaWO6 (x=0–1.9) have also been synthesized and characterized by powder X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and photoluminescence. XRD results reveal a phase transition from monoclinic to pseudo-cubic structure for x⩽0.2. All the compositions show broad charge transfer band and orange-red (MD and ED) emission. However, the relative intensity of the MD and ED depends on the Ba content present in the host lattice. Select compositions in this system of compounds could find potential application as orange-red phosphors for white light generation using blue/near-UV GaN-based light-emitting diodes (LEDs).

A series of orange-red-emitting A2CaWO6 (A=Sr, Ba) and Sr1.9−xBaxEu0.05Li0.05MoO6 (x=0–1.9) phosphor with double perovskite structure have been synthesized by solid-state reaction. All the compositions show broad charge transfer band and orange-red [magnetic dipole (MD) and electric dipole (ED)] emission. The red emission of Sr1.5Eu0.05Li0.05Ba0.4CaWO6 is found to be ∼4.5 times higher than that of commercial red phosphor (Nichia) under 465 nm excitation and hence this phosphor could be a potential candidate for white LED based on blue/NUV GaN LED.Figure optionsDownload as PowerPoint slide