Optimization of synthesis technique and luminescent properties in Eu3+-activated NaCaPO4 phosphor for solid state lighting applications

Europium activated NaCaPO4 phosphor has been synthesized by various synthesis techniques such as solid-state reaction (SSR), molten salt synthesis (MSS) and sol-gel combustion (SGC) method to optimize the synthesis procedure. The comparative investigations of structural and luminescent properties have been studied to know the best synthesis method. The XRD patterns and Rietveld refinement analysis of the synthesized phosphors confirmed the single phase orthorhombic structure of NaCaPO4. Excitation spectra indicate the strong absorption in near ultraviolet (n-UV) region and the emission spectra exhibit strong emission band at 595 nm corresponds to 5D0→7F1 transition under n-UV (λex=392 nm) excitation. The SGC route synthesized phosphor exhibit intense emission than that of the SSR and MSS method. Therefore, the effect of dopant (Eu3+) concentration on the emission intensity and concentration quenching mechanism has been discussed in detail for the Eu3+ doped NaCaPO4 phosphor synthesized by SGC method. The CIE chromaticity coordinates have been calculated for the phosphors synthesized by SSR, MSS and SGC methods to reveal the emitting color and also to know the utility of this phosphor for white LEDs.