Structural, morphological and photoluminescence studies of Ca7Mg2P6O24:RE3+(RE3+= Tb3+, Dy3+) nanophosphor for solid state illumination

Abstract

The Ca7Mg2P6O24:RE3+ (RE3+= Tb3+, Dy3+) nanophosphor material was synthesized by traditional wet chemical method. The XRD are used to determine phase and crystallinity of the synthesized sample; further FTIR, SEM, TEM, and PL properties were studied. The XRD pattern of prepared sample match well with standard JCPDS card no 00–020–0348, and it exhibits the rhombohedral structure along with space group R3c (161). The phosphate (PO4)3-group absorption band was observed at 990–1100 cm-1 in FTIR. Surface morphology (TEM analysis) reveals particle sizes in the range of 55–110 nm. The luminescence emission spectra of Ca7Mg2P6O24 phosphor activated by Tb3+ were studied at three different excitations: 352 nm, 370 nm, and 379 nm. The spectra show two emission peaks at 470 nm (blue) and 545 nm (green). These are due to the 5D4 → 7F6 and 5D4 → 7F5 transitions of Tb3+ ions. The highest intensity peak is located at 545 nm. The Ca7Mg2P6O24:Tb3+ phosphor's CIE chromaticity coordinates are (0.040, 0.316) at 491 nm and (0.265, 0.724) at 543 nm. These are in the blue and green areas on the edges of the CIE diagram, respectively. The photoluminescence emission spectra of Dy3+-doped Ca7Mg2P6O24 phosphor show two significant emission peaks located at 482 nm and 574 nm. These are caused by the 4F9/2 → 5H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, which produce blue and yellow light, respectively, with an excitation wavelength of 350 nm. The sharp peak position at 482 nm produces the strongest emission. The effect of concentration quenching in between the Dy3+-Dy3+ions and Tb3+-Tb3+ ions is due to dipole-dipole interaction. The CIE color coordinate is found to be (0.082, 0.156) at 482 nm and (0.471, 0.527) at 574 nm which lies in blue and yellow border of CIE diagram. The lifespan of Tb3+, Dy3+activated Ca7Mg2P6O24 nanophosphor of highest concentration is found to be 1.917 ms and 0.9985 ms respectively. On investigation, the synthesized Tb3+, Dy3+activated Ca7Mg2P6O24 nanophosphor can be potential for solid lightning devices & other display application.