Structural, luminescence, energy transfer mechanism, and photometric properties of Sm3+ -doped KYBO phosphors

Abstract

Potassium yttrium borate (KY(1-x)SmxBO3) referred as KYBO:Sm3+ phosphors with the varying of Sm3+ ions (x = 0.005, 0.01, 0.05, 0.1, 0.2, 0.3, 0.5 mol%) were fabricated via the solid-state reaction process. The structural and optical studies were systematically investigated via X-ray diffractometer (XRD), excitation (PLE), emission (PL) spectra, and decay curves. The structure of KYBO:Sm3+ phosphors is attributed to hexagonal with an average particle size of 34 nm. Scanning electron microscopy (SEM) image and energy dispersive X-ray analysis (EDAX) spectrum were also studied. The dominant excitation wavelength at 406 nm is ascribed to 6H5/2 → 4F7/2 transition and the emission spectra exhibits three peaks at 573, 609 and 656 nm belonging to 4G5/2 → 6H5/2, 7/2, 9/2 transitions of Sm3+ ions, respectively. Critical distance (Rc) and energy transfer rates (Arad) were also calculated. The energy transfer (ET) mechanism from luminescence spectra was proved by Dexter and Schulman theory. The decay of 4G5/2 level for KYBO:Sm3+ phosphors exhibited non-exponential nature by shortening the lifetime from 1.85 to 0.3 ms. Moreover, the photometric parameters such as color coordinates (0.557, 0.440), correlated color temperatures (CCT:1784–2552 K), and color purity (CP:93–96%) were also obtained for KYBO:Sm3+ phosphors. These results considered to be in the orange-red emission region for warm white light-emitting diodes.