The enhancement of emission intensity and enlargement of color gamut by a simple local structure substitution with highly thermal stability preserved

Abstract

The local crystal structure engineering becomes an important strategy to design new phosphors with enhanced optical and thermal performance of white light-emitting diodes. Herein, a series of Na3Sc2(PO4)3: Eu2+ and KyNa2.97-ySc2(PO4)3: 0.03Eu2+ phosphors were synthesized via traditional high temperature solid-state reaction method. X-ray powder diffraction analysis and Rietveld refinement provide insight in the detailed crystal structure. Furthermore, Eu2+ doped Na3Sc2(PO4)3 exhibits bright blue emission in 400–540 nm spectral range with a maximum value at ~ 460 nm under n-UV light excitation. The concentration quenching mechanism of Eu2+ in Na3Sc2(PO4)3 is certified to be a dipole-dipole interaction. Additionally, crystal structure tailoring is a potential strategy to design new phosphors for particular applications. Therefore, the effects of K+ substitution on the structure and photoluminescence of Eu2+ activated Na3Sc2(PO4)3 is presented in detail. Rietveld refinement data revealed that unit cell volume and Na/K–O band length increase when K+ occupy the Na+ sites. This sensitive local structure resulted in a considerable enhancement of the photoluminescence intensity of Eu2+. Incorporation of K+ in the crystal structure is a feasible route to realize fine-tuning of emission color and broaden the color gamut. In the meantime, Na2.7K0.27Sc2(PO4)3: 0.03Eu2+ phosphor exhibits excellent thermal stability at high temperature over a significant radiative recombination of energy transfer from traps to Eu2+. These results confirm that Na2.7K0.27Sc2(PO4)3: 0.03Eu2+ phosphor might be used as a blue component in n-UV chip activated white light-emitting diodes for the next-generation of indoor solid-state lighting applications.