Insights into structural and spectroscopic characterization of Sm3+ doped orange rich red emitting CsMgPO4 phosphors

Abstract

In the present study, Sm3+ activated inorganic orthophosphate CsMgPO4 (CSMP) phosphors were prepared by adopting a solid-state reaction method. The structural phase purity and morphological features were studied by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. The molecular structure and vibrational modes were substantiated with the Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy characterization. The optical bandgap of the host and Sm3+ doped phosphors was deduced from the diffused reflectance (DR) spectra with a typical value of 5.72 eV and a small variation is observed with increasing concentrations. A systematic study of photoluminescence (PL) properties of Sm3+ doped CSMP phosphors was carried out. From the room temperature excitation and emission spectra, it is found that the phosphor emits in the orange rich red light under the suitable excitation of 402 nm in the UV region and concentration quenching occurs at x = 0.02 doping level. The emission peaks observed at around 562, 598 and 644 nm confirm the characteristic Sm3+ 4f-4f transitions. The temperature-dependent photoluminescence (TD-PL) of the x = 0.02 (optimum doping) is recorded from 30 to 210 °C, showing good thermal stability even at 150 °C. The thermal quenching mechanisms are discussed based on the configuration coordinate model of excitation and emission. The prepared phosphors are found to exhibit near thermal stability compared to the commercially available red phosphors. PL decay time and quantum efficiency were measured. The colour coordinates are found to lie in the orangish-red region of the colour space. Thus the prepared phosphors CSMP:x Sm3+ can be useful as a red component in designing UV excitable chip-based phosphor-converted white LED applications.