Near Uv-Photons Excited Highly Pure and Thermally Stable Ca2b2o5: Sm3+ Phosphor for Filling the Amber Gap

Abstract

Un-doped and a series of Sm3+ ion-doped orange-red emitting Ca2(1-x)B2O5:2xSm3+ (x = 0.005-0.025 mol) phosphors were synthesized and explored for their potential to fill the amber gap. Structural, thermal, spectral, luminescence, and temperature-dependent luminescence studies of the obtained phosphors were carried out to investigate the synthesized phosphors. The powder X-ray diffraction and Rietveld refinement results confirmed the formation of the monoclinic phase of Ca2B2O5. The room temperature photoluminescence study revealed that under 405 nm excitation, the prepared phosphor shows four characteristic emissions due to the 4f-4f transitions i.e.4G5/2 → 6H5/2 (568 nm), 6H7/2 (607 nm), 6H9/2 (650 nm) and 6H11/2 (712 nm). The color purity of the prepared phosphors was determined to be 97.7% with the Commission International de l'Eclairage coordinates of (0.60, 0.40) that correspond to a strong orange-red emission located in the amber gap. Moreover, temperature-dependent luminescence studies depicted that the phosphor is highly stable, at 150 °C retaining 89% of its luminescence intensity compared to room temperature, the thermal stability was further verified by thermogravimetric analysis of the phosphors which revealed high thermal stability with no weight loss upto 900 °C. Thus, the promising experimental result suggests that the extremely stable orange-red emitting Ca2B2O5:Sm3+ phosphor can be a potential choice to fill the amber gap in light-emitting diodes.

Keywords: Amber-gap, photoluminescence, phosphor, Borates