Red emitting non-rare earth doped LiMgBO3 phosphor for light emitting diodes

Abstract

Cost-effective non-rare earth doped phosphor materials, particularly Mn4+ activated nitrides and fluorides, are emerging as prospective alternatives to rare earth doped red-emitting phosphor materials for light emitting diodes. Yet, it is challenging to prepare such cost-effective and high purity red-emitting non-rare earth doped phosphors because of their broad emission profiles and difficulties in the synthesis of nitrides and fluorides. In order to overcome the challenges faced in developing cost-effective and efficient materials for lighting solutions, we report a new red-emitting Mn4+ doped LiMgBO3 phosphor synthesized by solution combustion and solid-state routes. The phosphors had broad excitation bands in the UV (200–400 nm) and blue (400–560 nm) regions of the spectrum. Under both UV/visible excitation, the phosphors emit at 664 and 669 nm for the materials synthesized through solid-state and combustion route respectively and the corresponding full width at half maxima were 94 nm and 40 nm. The photoluminescence (PL) intensity of the phosphor synthesized by combustion method, was found to be six times higher than that synthesized through the solid-state route. The effect of crystal field environment on the PL properties, evaluated from crystal field strength and the Racah parameters (B and C), showed that Mn4+ ions were present in a strong octahedral field for both synthesis methods. X-ray photoelectron spectroscopy confirmed the existence of all the elements on the surface of the phosphors. Temperature dependent PL studies and the photometric properties such as color purity, International Commission on Illumination chromaticity coordinates of the phosphors were also evaluated.