Synthesis and photoluminescence properties of NaCaPO4:Eu2+ phosphor for solid state lighting

A novel method to prepare orthophosphate NaCaPO4:Eu2+ phosphor for white light-emitting diodes (w-LEDs) is given in this paper. Phosphor was successfully synthesized by Pechini (citrate gel) method which is efficient than conventional high temperature solid state reaction. X-ray powder diffraction (XRD) analysis confirmed the single phase formation of NaCaPO4:Eu2+ with orthorhombic crystal structure (also called as rhenanite or β-NaCaPO4). Luminescence results showed that the phosphor could be efficiently excited by near UV with intense excitation peak at 394 nm and exhibited two bright red emission narrow bands in the wavelength range 575 nm to 640 nm corresponding to 5D0 → 7F1 and 5D0 → 7F2 transitions of Eu3+ respectively in NaCaPO4:Eu3+ with maximum intensity peak at 595 nm without reduction. When Eu3+ in NaCaPO4:Eu3+ is reduced by carbo-thermal reduction to Eu2+ it gives intense broad band emission at 563 nm resulting green emitting phosphor. Hence both of phosphors could be useful for solid state lighting and light-emitting diode (LED) application for fabrication of w-LED’s.