Photoluminescence studies of ytterbium doped calcium sulphate nanophosphors for display applications

CaSO₄:Yb³⁺(1, 3 and 5 mol%) nanophosphors were synthesized by co-precipitation method and characterized by powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM), Raman and photoluminescence (PL) techniques. PXRD pattern of all CaSO₄:Yb³⁺ nanophosphors confirmed monoclinic phase (JCPDS Card no. 21-0816 with space group C2/c (No.15)). FTIR spectra showed absorption bands at 603, 1174, 1618, 2230, 2933 and 3557 cm⁻¹. SEM images clearly reveal that the CaSO₄:Yb³⁺ phosphors composed of nanobar morphology. The average width of the nanobar was found to be in the range of 60–80 nm and a length up to few μm. EDS analysis confirms the chemical composition of the samples. TEM image showed that CaSO₄:Yb³⁺ (1 mol%) consists of nanobar with average width of about 50 nm. Raman spectra of CaSO₄:Yb³⁺nanophosphor showed peaks at ∼351, 621, 642 and 1016 cm⁻¹. The emission spectra of CaSO₄:Yb³⁺nanophosphors showed a prominent emission band at 1075 nm under 880 nm excitation. The synthesised phosphor may be used in display and solid state applications. (paper)